Multilayered volume hologram structure, and label for making multilayered volume hologram structure

ABSTRACT

A multilayered volume hologram structure of the invention comprises a substrate  2  for a certificate or the like, and an adhesive layer  5,  a volume hologram layer  5  and a surface protective film  7  laminated on the substrate in the described order. When a multilayer structure consisting of the volume hologram layer  5  and surface protective layer  5  is forcibly released from the substrate for the purpose of making a photograph replacement or falsifying a personal information area, the volume hologram image can break down certainly, thereby ensuring prevention of falsification. A multilayered volume hologram structure-making label is useful for making a multilayered volume hologram structure.

TECHNICAL FIELD

[0001] The present invention relates generally to a multilayered volumehologram structure comprising a transparent image bearing hologram,which is pasted on a surface of a photograph or personal informationarea attached to ID cards, exam cards, passports, etc. for the purposeof ensuring security and a label for making such a multilayered volumehologram structure, and more particularly to a multilayered volumehologram structure which cannot possibly be fraudulently altered orotherwise falsified, and a label for making such a multilayered volumehologram structure.

[0002] In recent years, means for preventing fraudulent alternation orfalsification of identity cards, etc. have been strongly demanded, forinstance, so as to certainly identify who carries an ID card as who ischaracterized by identifying data born thereon. Such falsificationpreventive techniques, for instance, are disclosed in JM-B 5-48215 andJP-A 5-201181 wherein an image bearing hologram is used. The image ofthe image bearing hologram has the same function as an engraving or thelike on a conventional ID card or the like.

[0003] Especially according to the means disclosed in the latterpublication, when the protective film is stripped off for the purpose offalsification or the like, the hologram layer fractures due to itssoftness to make it impossible to reconstruct the hologram image,thereby preventing falsification as by making a photograph replacement.When a rigid plastic film is used as the surface protective film,however, the hologram layer is often perfectly stripped off followingthe surface protective film. In this case, there is no sign of aphotograph replacement or falsification of information. It is thusstrongly demanded to improve this prior art means in such a way that thefunction of preventing falsification is much more improved for thepurpose of ensuring security.

DISCLOSURE OF THE INVENTION

[0004] According to a first aspect of the invention, there is provided amultilayered volume hologram structure comprising a substrate for acertificate or the like, and a first adhesive layer, a volume hologramlayer and a surface protective film laminated on said substrate in thedescribed order, characterized in that a peel strength, with which amultilayer structure consisting of said volume hologram layer and saidsurface protective film is peeled from said substrate, is greater than abreaking strength or a tensile strength at 1% elongation of saidmultilayer structure consisting of said volume hologram layer and saidsurface protective film.

[0005] The multilayered volume hologram structure according to the firstaspect of the invention is further characterized in that the peelstrength, with which said multilayer structure consisting of said volumehologram layer and said surface protective film is peeled from saidsubstrate (e.g., a photograph), is 0.1 Kg/25 mm to 5.0 Kg/25 mm, and amultilayer structure comprising said first adhesive layer, said volumehologram layer and said surface protective film laminated on saidsubstrate in the described order has a breaking strength or a tensilestrength at 1% elongation of 0.01 Kg/mm² to 5.0 Kg/mm².

[0006] The multilayered volume hologram structure according to the firstaspect of the invention is further characterized in that anotheradhesive layer is interleaved between said volume hologram layer andsaid surface protective film.

[0007] The multilayered volume hologram structure according to the firstaspect of the invention is further characterized in that said surfaceprotective film is subjected to a hard coat treatment on a surfacethereof.

[0008] The multilayered volume hologram structure according to the firstaspect of the invention is further characterized in that said surfaceprotective film is subjected to a release treatment on a surfacethereof.

[0009] The present invention also provides a label for making themultilayered volume hologram structure according to the first aspect ofthe invention, characterized by comprising a release paper and a firstadhesive layer, a volume hologram layer and a surface protective filmlaminated on said release paper in the described order, said label beingpasted on a substrate for a certificate or the like upon removal of saidrelease paper.

[0010] The label for making the multilayered volume hologram structureaccording to the first aspect of the invention is further characterizedin that a peel strength, with which a multilayer structure consisting ofsaid volume hologram layer and said surface protective film is peeledfrom said substrate, is 0.1 Kg/25 mm to 5.0 Kg/25 mm, and a multilayerstructure comprising said first adhesive layer, said volume hologramlayer and said surface protective film laminated in the described orderhas a breaking strength or a tensile strength at 1% elongation of 0.01Kg/mm² to 5.0 Kg/mm².

[0011] The label for making the multilayered volume hologram structureaccording to the first aspect of the invention is further characterizedin that said volume hologram layer and said surface protective film arelaminated together with said first adhesive layer interleavedtherebetween.

[0012] The volume hologram structure according to the first aspect ofthe invention ensures prevention of falsification because, immediatelyupon making a photograph replacement or falsification of the informationarea, the volume hologram image breaks down certainly. With the labelfor making the multilayered volume hologram structure according to thefirst aspect of the invention, it is easy to make the multilayeredvolume hologram structure according to the first aspect of theinvention.

[0013] According to a second aspect of the invention, there is provideda multilayered volume hologram structure comprising a substrate, and afirst adhesive layer, a volume hologram layer, a second adhesive layerand a surface protective film laminated on said substrate in thedescribed order, characterized in that said second adhesive layer isweaker in adhesion than said first adhesive layer, and when said surfaceprotective film is released from said multilayered volume hologramstructure in a given releasing direction, a releasing line is producedin a direction at right angles with respect to said releasing direction.

[0014] According to the second aspect of the invention, there is alsoprovided a multilayered volume hologram structure comprising asubstrate, and a third adhesive layer, a colored sheet, a first adhesivelayer, a volume hologram layer, a second adhesive layer and a surfaceprotective film laminated on said substrate in the described order,characterized in that said second adhesive layer is weaker in adhesionthan said first adhesive layer and said third adhesive layer, and whensaid surface protective film is released from said multilayered volumehologram structure in a given releasing direction, a releasing line isproduced in a direction at right angles with respect to said releasedirection.

[0015] The second multilayered volume hologram structure of theinvention is also characterized in that a peel strength, with which saidsurface protective film is released from said multilayered volumehologram structure, is 0.001 Kg/25 mm to 0.1 Kg/25 mm, and a peelstrength between said substrate and said volume hologram layer is 0.1Kg/25 mm to 5.0 Kg/25 mm.

[0016] The second multilayered volume hologram structure of theinvention is further characterized in that said volume hologram layer ismade up of a photosensitive material used for recording a dry type ofvolume phase hologram, which comprises a matrix polymer, aphotopolymerizable compound, a photopolymerization initiator and asensitizing dye.

[0017] One label for making the second multilayered volume hologramstructure of the invention is a multilayered volume hologram structurecomprising a release paper, and a first adhesive layer, a volumehologram layer, a second adhesive layer and a surface protective filmlaminated on said release paper in the described order, characterized inthat said second adhesive layer is weaker in adhesion than said firstadhesive layer, and when said surface protective film is released fromsaid multilayered volume hologram structure in a given releasingdirection, a releasing line is produced in a direction at right angleswith respect to said releasing direction.

[0018] Another label for making the second multilayered volume hologramstructure of the invention is a multilayered volume hologram structurecomprising a release paper, and a third adhesive layer, a colored sheet,a first adhesive layer, a volume hologram layer, a second adhesive layerand a surface protective film laminated on said substrate in thedescribed order, characterized in that said second adhesive layer isweaker in adhesion than said first adhesive layer and said thirdadhesive layer, and when said surface protective film is released fromsaid multilayered volume hologram structure in a given releasingdiretion, a releasing line is produced in a direction at right angleswith respect to said releasing direction.

[0019] When the surface protective film is released from the secondmultilayered volume hologram structure of the invention, releasinglayers are produced. When the recorded hologram is copied, the copy canbe distinguished from the original hologram because the releasing layersare copied at the same time. Even when a hologram with the releasinglines formed thereon is pasted on another substrate for forgingpurposes, the hologram can be distinguished from the original hologrambecause of the presence of the releasing lines. Thus, prevention offalsification can be ensured. With the label for making the secondmultilayered volume hologram structure of the invention, the secondmultilayered volume hologram structure of the invention can be easilyprepared.

[0020] According to a third aspect of the invention, there is providedone multilayered volume hologram structure comprising a substrate for acertificate or the like, and a heat sealing layer, a volume hologramlayer, an-adhesive layer and a surface protective film laminated on saidsubstrate, characterized in that the whole surface of said multilayeredvolume hologram structure is heat-sealed.

[0021] According to the third aspect of the invention, there is providedanother multilayered volume hologram structure comprising a certificatefor a certificate or the like, and an adhesive layer, a volume hologramlayer, a heat sealing layer and a surface protective layer laminated onsaid substrate, characterized in that said volume hologram layer and anend portion thereof are coated with said surface protective film, saidvolume hologram layer is laminated on said substrate, and only theoverall peripheral end of said multilayered volume hologram structureincluding the overall peripheral end of said volume hologram layer isheat-sealed.

[0022] The third multilayered volume hologram structure of the inventionis characterized in that heat sealing has been done at 100° C. to 180°C.

[0023] One label for making the third multilayered volume hologramstructure of the invention is characterized by comprising a releasepaper, and a heat sealing layer, a volume hologram layer, an adhesivelayer and a surface protective layer laminated on said release paper inthe described order.

[0024] Another label for making the third multilayered volume hologramstructure of the invention is characterized by comprising a releasepaper, and an adhesive layer, a volume hologram layer, a heat sealinglayer and a surface protective film laminated on said release paper inthe described order, a size of said surface protective film being suchthat, upon said label laminated on a substrate for a certificate or thelike, said surface protective film covers said volume hologram layerincluding a whole periphery of an end thereof.

[0025] When the third multilayered volume hologram structure of theinvention is forcibly delaminated, the volume hologram display layerbreaks down certainly, thereby ensuring prevention of falsification asby making a photograph replacement. With the label for making the thirdmultilayered volume hologram layer of the invention, the thirdmultilayered volume hologram structure can be easily prepared.

[0026] A fourth multilayered volume hologram structure of the inventionis characterized by comprising a substrate and a hologram layer pastedon said substrate, said hologram layer being provided with a surfaceprotective-film on a surface thereof, and further including a secondadhesive layer for bonding together said surface protective film andsaid hologram layer and a first adhesive layer for bonding together saidhologram layer and said substrate, either one of said adhesive layershaving an adhesion force profile in its own plane.

[0027] A label for making the fourth multilayered volume hologramstructure of the invention is a label used for making the fourthmultilayered volume hologram structure of the invention characterized bycomprising a release paper, and a first adhesive layer, a volumehologram layer, a second adhesive layer and a surface protective filmlaminated on said release paper in the described order, said label beingpasted on a substrate for a certificate or the like upon removal of saidrelease paper therefrom, and either one of said first adhesive layer andsaid second adhesive layer having an adhesive force profile in its ownplane.

[0028] When the fourth multilayered volume hologram structure of theinvention is forcibly delaminated, the volume hologram display layerbreaks down certainly, thereby ensuring prevention of falsification asby making a photograph replacement. With the label for making the fourthmultilayered volume hologram layer of the invention, the fourthmultilayered volume hologram structure can be easily prepared.

[0029] One embodiment of a fifth multilayered volume hologram structureof the invention comprises a substrate, and a first adhesive layer, avolume hologram layer, a second adhesive layer and a surface protectivefilm laminated on said substrate in the described order, and ischaracterized in that microcapsules, each encapsulated with a materialcapable of breaking said hologram layer, are incorporated in saidadhesive layers, so that said microcapsules can break down upondelamination of said multilayered volume hologram structure.

[0030] Another embodiment of the fifth multilayered volume hologramstructure of the invention comprises a substrate, and a third adhesivelayer, a coloring sheet, a first adhesive layer, a volume hologram, asecond adhesive layer and a surface protective film laminated on saidsubstrate in the described order, and is characterized in thatmicrocapsules, each encapsulated with a material capable of breakingsaid volume hologram layer, are incorporated in said first and secondadhesive layers disposed adjacent to said hologram layer, so that saidmicrocapsules can break down upon delamination of said multilayeredvolume hologram structure.

[0031] The fifth multilayered volume hologram structure of the inventionis also characterized in that a material forming said volume hologramlayer comprises a matrix polymer, a photopolymerizable compound, aphotopolymerization initiator and a sensitizing dye, and said materialcapable of breaking said volume hologram layer comprises an organicsolvent having a solubilizing action on said volume hologram layerforming material and/or a plasticizer having a swelling action on saidvolume hologram layer forming material.

[0032] One embodiment of a label for making the fifth multilayeredvolume hologram structure of the invention is a label used for makingthe first embodiment of the aforesaid fifth multilayered volume hologramstructure. This label comprises a release paper, and a first adhesivelayer, a volume hologram layer, a second adhesive layer and a surfaceprotective film laminated on said release paper in the described order,and is characterized in that microcapsules, each encapsulated with amaterial capable of breaking said volume hologram layer, areincorporated in said adhesive layers, so that said microcapsules canbreak down upon delamination of said multilayered volume hologramstructure.

[0033] Another embodiment of the label for making the fifth multilayeredvolume hologram structure of the invention is a label for making thesecond embodiment of the fifth multilayered volume hologram structure.This label comprises a release paper, and a third adhesive layer,a-coloring sheet, a first adhesive layer, a volume hologram, a secondadhesive layer and a surface protective film laminated on said releasepaper in the described order, and is characterized in thatmicrocapsules, each encapsulated with a material capable of breakingsaid volume hologram layer, are incorporated in said adhesive layersdisposed adjacent to said volume hologram layer, so that saidmicrocapsules can break down upon delamination of said multilayeredvolume hologram structure.

[0034] The label for making the aforesaid fifth multilayered volumehologram structure is characterized in that a material forming saidvolume hologram layer comprises a matrix polymer, a photopolymerizablecompound, a photopolymerization initiator and a sensitizing dye, andsaid material capable of breaking said volume hologram layer comprisesan organic solvent having a solubilizing action on said volume hologramlayer forming material and/or a plasticizer having a swelling action onsaid volume hologram layer forming material.

[0035] When, upon a release from the adhesive layers, the fifthmultilayered volume hologram structure of the invention is re-laminatedthereon, the volume hologram layer breaks down on contact with thevolume hologram layer breaking material coming out of the microcapsulesupon a breakdown. As a result, even when the photograph pasted on themultilayered volume hologram structure is replaced by anotherphotograph, such a photograph replacement can be detected by identifyingthe presence of the broken hologram. It is thus possible to make sure ofprevention of falsification. With the label for making the fifthmultilayered volume hologram structure, the fifth multilayered volumehologram structure can be easily prepared.

[0036] One embodiment of a sixth multilayered volume hologram structureof the invention is characterized by comprising a substrate for acertificate or the like, and an adhesive layer, a volume hologram layercontaining fine particles having an average primary particle size of 1nm to 100 nm and used in an amount of 10 parts by weight to 100 parts byweight per 100 parts by weight of a photosensitive material, and asurface protective film laminated on said substrate in the describedorder.

[0037] This structure is also characterized in that said fine particlesare each a fluorescent fine particle emitting fluorescence uponirradiation with ultraviolet radiation.

[0038] Another embodiment of the sixth multilayered volume hologramstructure of the invention is characterized by comprising a substratefor a certificate or the like, and an adhesive layer, a volume hologramlayer containing plastic particles or glass beads having a refractiveindex substantially equal to that of a photosensitive material and usedin an amount of 10 parts by weight to 100 parts by weight per 100 partsby weight of said photosensitive material, and a surface protective filmlaminated on said substrate in the described order.

[0039] The aforesaid sixth multilayered volume hologram structure isalso characterized in that said volume hologram layer and said surfaceprotective film are laminated together with an additional adhesive layerinterleaved therebetween.

[0040] One embodiment of a label for making the sixth multilayeredvolume hologram structure is characterized by comprising a releasepaper, and an adhesive layer, a volume hologram layer containing fineparticles having an average primary particle size of 1 nm to 100 nm andused in an amount of 10 parts by weight to 100 parts by weight per 100parts by weight of a photosensitive material, and a surface protectivefilm laminated on said release paper in the described order.

[0041] This label is also characterized in that said fine particles areeach a fluorescent fine particles emitting fluorescence upon irradiationwith ultraviolet radiation.

[0042] Another embodiment of the label for making the sixth multilayeredvolume hologram structure of the invention is characterized bycomprising a release paper, and an adhesive layer, a volume hologramlayer containing plastic particles or glass beads having a refractiveindex substantially equal to that of a photosensitive material and usedin an amount of 10 parts by weight to 100 parts by weight per 100 partsby weight of said photosensitive material, and a surface protective filmlaminated on said substrate in the described order.

[0043] This label is also characterized in that said volume hologramlayer and said surface protective film are laminated together with anadditional adhesive layer interleaved therebetween.

[0044] When the sixth multilayered volume hologram structure of theinvention is forcibly delaminated, the volume hologram layer breakssown. It is thus possible to make sure of prevention of falsification asby making a photograph replacement. With the label for making the sixthmultilayered volume hologram structure, the sixth multilayered volumehologram structure can be easily prepared.

[0045] One embodiment of a seventh multilayered volume hologramstructure of the invention is characterized by comprising a substratefor a certificate or the like, and an adhesive layer, a volume hologramlayer, a resin layer containing a monomer or a plasticizer and a surfaceprotective film laminated on said substrate in the described order.

[0046] This multilayered volume hologram structure is also characterizedin that said resin layer containing a monomer or a plasticizer and saidsurface protective film are laminated together with an additionaladhesive layer interleaved therebetween.

[0047] Another embodiment of the seventh multilayered volume hologramstructure of the invention is characterized by comprising a substratefor a certificate or the like, and an adhesive layer, a volume hologramlayer, a brittle layer, an adhesive layer and a surface protective filmlaminated on said substrate in the described order.

[0048] One embodiment of a label for making the seventh multilayeredvolume hologram structure of the invention is characterized bycomprising a release paper, and an adhesive layer, a volume hologramlayer, a resin layer containing a monomer or a plasticizer and a surfaceprotective film laminated on said release paper in the described order.

[0049] This multilayered volume hologram structure is also characterizedin that said monomer or plasticizer-containing resin layer and saidsurface protective film are laminated together with an additionaladhesive layer interleaved therebetween.

[0050] Another embodiment of the label for making the seventhmultilayered volume hologram structure of the invention is characterizedby comprising a release paper, and an adhesive layer, a volume hologramlayer, a brittle layer, an adhesive layer and a surface protective filmlaminated on said release paper in the described order.

[0051] When the seventh multilayered volume hologram structure of theinvention is forcibly delaminated, the volume hologram layer remains onthe substrate such as a photograph. It is thus possible to make use ofthe brittleness of the hologram layer to ensure prevention offalsification as by making a photograph replacement. With the label formaking the seventh multilayered volume hologram structure, the seventhmultilayered volume hologram structure can be easily prepared.

[0052] One embodiment of an eighth multilayered volume hologramstructure of the invention is characterized by comprising a substratefor a certificate or the like, and a first adhesive layer, a volumehologram layer and a surface protective film laminated on said substratein the described order, and further including between said volumehologram layer and said surface protective film a patterned area forvarying relative adhesion between said volume hologram layer and saidsurface protective film in a site-dependent manner, so that upon anintentional release of a multilayer structure from said substrate, saidvolume hologram layer is broken or elongated while said volume hologramlayer is separated into a portion adhering to said substrate and aportion adhering to said surface protective film.

[0053] This multilayered volume hologram structure is also characterizedin that upon irradiation with ultraviolet radiation or heating, one ofsaid volume hologram layer or said surface protective film showsadhesion to the other or the relative adhesion between said volumehologram layer and said surface protective film decreases.

[0054] Another embodiment of the eighth multilayered volume hologramstructure of the invention is characterized by comprising a substratefor a certificate or the like, and a first adhesive layer, a volumehologram layer, a second adhesive layer and a surface protective filmlaminated on said substrate in the described order, and furtherincluding between said second adhesive layer and said surface protectivefilm a patterned area for varying mutual adhesion between said secondadhesive layer and said surface protective film in a site-dependentmanner, so that upon an intentional release of an multilayer structurefrom said substrate, said volume hologram layer is broken or elongatedwhile said volume hologram layer is separated into a portion adhering tosaid substrate and a portion adhering to said surface protective film.

[0055] This multilayered volume hologram structure is also characterizedin that said patterned area for varying said adhesion in asite-dependent manner is a pattern of release agent layer.

[0056] Further, this multilayered volume hologram structure ischaracterized in that said patterned area for varying said adhesion in asite-dependent manner is an adhesion-enhancing pattern of primer layer.

[0057] Furthermore, this multilayered volume hologram structure ischaracterized in that said patterned area for varying said adhesion in asite-dependent manner is obtained by treating a surface of said surfaceprotective film to be laminated in such a way that said surface iseasily bondable.

[0058] Yet another embodiment of the eighth multilayered volume hologramstructure of the invention is characterized by comprising a substratefor a certificate or the like, and a first adhesive layer, a volumehologram layer, a second adhesive layer and a surface protective filmlaminated on said substrate in the described order, and furtherincluding between said first adhesive layer and said volume hologramlayer a patterned area for varying relative adhesion between said firstadhesive layer and said volume hologram layer in a site-dependentmanner, so that upon an intentional release of a multilayer structurefrom said substrate, said volume hologram layer is broken or elongatedwhile said volume hologram layer is separated into a portion adhering tosaid substrate and a portion adhering to said surface protective film.

[0059] One embodiment of a label for making the eighth multilayeredvolume hologram structure of the invention is a label used for makingthe aforesaid eighth multilayered volume hologram structure. Theaforesaid label is characterized by comprising a release paper, and afirst adhesive layer, a volume hologram layer and a surface protectivefilm laminated on said substrate in the described order, and furtherincluding between said volume hologram layer and said surface protectivefilm a patterned area for varying relative adhesion between said volumehologram layer and said surface protective film in a site-dependentmanner. This label is pasted on a substrate for a certificate or thelike upon a release of said release paper therefrom.

[0060] Another embodiment of the label for the eighth multilayeredvolume hologram structure of the invention is a label used for makingthe second embodiment of the eighth multilayered volume hologramstructure. The aforesaid label is characterized by comprising a releasepaper, and a first adhesive layer, a volume hologram layer, a secondadhesive layer and a surface protective film laminated on said substratein the described order, and further including between said secondadhesive layer and said surface protective film a patterned area forvarying relative adhesion between said second adhesive layer and saidsurface protective film in a site-dependent manner. This label is pastedon a substrate for a certificate or the like upon a release of saidrelease paper therefrom.

[0061] Yet another embodiment of the label for the eighth multilayeredvolume hologram structure of the invention is a label used for makingthe third embodiment of the eighth multilayered volume hologramstructure. The aforesaid label is characterized by comprising a releasepaper, and a first adhesive layer, a volume hologram layer, a secondadhesive layer and a surface protective film laminated on said substratein the described order, and further including between said firstadhesive layer and said volume hologram layer a patterned area forvarying relative adhesion between said second adhesive layer and saidvolume hologram layer in a site-dependent manner. This label is pastedon a substrate for a certificate or the like upon a release of saidrelease paper therefrom.

[0062] With the eighth multilayered volume hologram layer according tothe invention, the volume hologram layer can break down certainly uponan intentional photograph replacement or falsification of an personalinformation area. It is thus possible to make sure of prevention offalsification. With the label for making the eighth multilayered volumehologram structure, the eighth multilayered volume hologram structurecan be easily prepared.

BRIEF DESCRIPTION OF THE DRAWINGS

[0063]FIG. 1 is a front schematic of one embodiment of the firstmultilayered volume hologram structure of the invention.

[0064]FIG. 2 is a sectional schematic taken along the line A-A in FIG.1, showing the first multilayered volume hologram structure of theinvention.

[0065]FIG. 3 is a schematic illustrative of another embodiment of thefirst multilayered volume hologram structure of the invention.

[0066]FIG. 4 is a schematic illustrative of how to release the firstmultilayered volume hologram structure of the invention.

[0067]FIG. 5 is a schematic illustrative of how to release the firstmultilayered volume hologram structure of the invention.

[0068]FIG. 6 is a sectional schematic illustrative of the label formaking the first multilayered volume hologram structure of theinvention.

[0069]FIG. 7 is a sectional schematic illustrative of one embodiment ofthe second multilayered volume hologram structure of the invention.

[0070]FIG. 8 is a sectional schematic illustrative of one embodiment ofthe second multilayered volume hologram structure of the invention.

[0071]FIG. 9(a) is a sectional view illustrative of how to release thesurface protective film from the second multi-layered volume hologramstructure of the invention, and

[0072]FIG. 9(b) is a perspective view illustrative of the same.

[0073]FIG. 10 is a sectional schematic illustrative of the label formaking the second multilayered volume hologram structure of theinvention.

[0074]FIG. 11 shows the results of measuring the state of changes in thepeeling strength with which the surface protective film is released fromthe multilayered volume hologram structure of the invention.

[0075]FIG. 12 is a sectional schematic illustrative of one embodiment ofthe third multilayered volume hologram structure of the invention.

[0076]FIG. 13 is a sectional schematic illustrative of anotherembodiment of the third multilayered volume hologram structure of theinvention.

[0077]FIG. 14 is a schematic illustrative of the heat-sealed portion inthe second embodiment of the third multilayered volume hologramstructure of the invention.

[0078]FIG. 15 is a schematic illustrative of one embodiment of the labelfor making the third multilayered volume hologram structure of theinvention.

[0079]FIG. 16 is a schematic illustrative of another embodiment of thelabel for making the third multilayered volume hologram structure of theinvention.

[0080]FIG. 17 is a schematic illustrative of the first embodiment of thefourth multilayered volume hologram structure of the invention.

[0081]FIG. 18 is a schematic illustrative of how the hologram 3 isreleased from the structure shown in FIG. 17(a) from a direction shownby B.

[0082]FIG. 19 is a schematic illustrative of the second embodiment ofthe fourth multilayered volume hologram structure of the invention.

[0083]FIG. 20 is a schematic illustrative of the third embodiment of thefourth multilayered volume hologram structure of the invention.

[0084]FIG. 21 is a schematic illustrative of the fourth embodiment ofthe fourth multilayered volume hologram structure of the invention.

[0085]FIG. 22 is a schematic illustrative of one embodiment of the fifthmultilayered volume hologram structure of the invention.

[0086]FIG. 23 is a schematic illustrative of another embodiment of thefifth multilayered volume hologram structure of the invention.

[0087]FIG. 24 is a schematic illustrative of the label for making thefifth multilayered volume hologram structure of the invention.

[0088]FIG. 25 is a schematic illustrative of the sixth multilayeredvolume hologram structure of the invention.

[0089]FIG. 26 is a schematic illustrative of the third embodiment of thesixth multilayered volume hologram structure of the invention.

[0090]FIG. 27 is a sectional schematic illustrative of the label formaking the sixth multilayered volume hologram structure of theinvention.

[0091]FIG. 28 is a sectional schematic illustrative of one embodiment ofthe seventh multilayered volume hologram structure of the invention.

[0092]FIG. 29 is a sectional schematic illustrative of anotherembodiment of the seventh multilayered volume hologram structure of theinvention.

[0093]FIG. 30 is a sectional schematic illustrative of the label formaking the seventh multilayered volume hologram structure of theinvention.

[0094]FIG. 31 is a schematic illustrative of the first embodiment of theeighth multilayered volume hologram structure of the invention.

[0095]FIG. 32 is a plan schematic illustrative of the patterned area forvarying adhesion.

[0096]FIG. 33 is a schematic illustrative of the second embodiment ofthe eighth multilayered volume hologram structure of the invention.

[0097]FIG. 34 is a schematic illustrative of the third embodiment of theeighth multilayered volume hologram structure of the invention.

[0098]FIG. 35 is a schematic illustrative of how to release the eighthmultilayered volume hologram structure of the invention.

[0099]FIG. 36 is a sectional schematic illustrative of the label formaking the eighth multilayered volume hologram structure of theinvention.

[0100]FIG. 37 is a schematic illustrative of how to record andreconstruct a Lippmann hologram.

[0101]FIG. 38 is a schematic illustrative of how to record andreconstruct a transmission type volume hologram.

BEST MODE FOR CARRYING OUT THE INVENTION

[0102] The first multilayered volume hologram structure of the inventionand the label for making the same are first explained.

[0103]FIG. 1 is a front schematic illustrative of the first multilayeredvolume hologram structure of the invention, and FIG. 2 is a sectionalschematic taken along the A-A line in FIG. 1. Reference numeral 1represents a first multilayered volume hologram structure , 2 asubstrate for a certificate or the like, 3 paste for pasting aphotograph or an information area on the multilayered volume hologramstructure, 4 a photograph of face, 4′ a personal information area, 5′ afirst adhesive layer, 6 a volume hologram layer, 7 a surface protectivefilm, and 8 personal information.

[0104] The multilayered volume hologram structure shown in FIG. 1 takesthe form of a certificate for examination. The personal information 8such as a name and an examinee's number is put down on the substrate 2,and the photograph of face 4 and information area 4′ are pasted on thesubstrate 2. Identifying data about the individual who carries thecertificate are born on the information area 4. The information area 4in a seal form is pasted on the substrate 2, as in the case of thephotograph. A school name or badge bearing hologram image is recorded onthe volume hologram layer 6 with interference fringes corresponding to ahologram interference pattern.

[0105] In this regard, it is to be noted that the personal information 8may be recorded at a position on which the hologram 3 is to be pasted orother position. In other words, the personal information may be recordedat any desired position on the substrate 2 as occasion arises. Thisinformation may be recorded on the substrate 2 by known means such ashandwriting, typing, and printing using toner, a thermal transferribbon, a type ribbon, and printing ink, for instance. The informationmay also be magnetically recorded. When the substrate 2 is formed ofplastic or metal material, the information may be recorded thereon byembossing.

[0106] In the first multilayered volume hologram structure of theinvention, the photograph of face 4 and information area 4′ are pastedon the substrate 2 with photographic paste 3, as can be seen from FIG.2. The first adhesive layer 5′, volume hologram layer 6 and surfaceprotective film 7 are laminated on the substrate 2 and astride thephotograph of face 4 and information area 4′ in the described order.

[0107] For the substrate 2, a sheet or film form of paper, syntheticpaper, synthetic resin or metal may be used. Use may also be made of acard such as an ID card or a booklet form of credit card or passport, onwhich given pieces of information are recorded. The photographic paste 3may have an adhesion strength with which the photograph 4 or informationarea 4′ cannot be detached from the substrate 2 when a multilayerstructure composed of the volume hologram layer and surface protectivefilm is forcibly stripped from the substrate, and so may be generallyavailable starch paste or synthetic paste.

[0108] For the photograph of face 4, known photographic materialsrepresented by silver salt, sublimation transfer images, etc. may beused. Instead of the face of an individual, an image indicating thefinger print, palm print, etc. of the individual may be used. When, forinstance, the certificate is an admission certificate for a sport eventor the like, monochromatic or polychromatic numerals, characters, etc.may be indicated on the information area 4′ of the certificate.Furthermore, the name of the site, whether or not the individual whocarries the certificate is a player, qualifications, sponsor'sinstructions, etc. may be indicated-on the information area 4′.

[0109] The first adhesive layer 5′ is re-bondable to the substrate 2upon removal of the release paper (to be described later) from the labelfor making the first multi-layered volume hologram structure of theinvention. For instance, this adhesive layer 5′ is formed of acrylicresin, acrylic ester resin, and vinyl acetate resin or their copolymersas well as styrene-butadiene copolymer, natural rubber, casein, gelatin,rosin ester, terpene resin, phenolic resin, styrene resin,coumarone-indene resin, polyvinyl ether, and silicone resin. Theadhesive layer 5′ may also be formed of adhesives based onα-cyanoacrylate, silicone, maleimide, styrol, polyolefin, resorcinol,and polyvinyl ether as well as heat-sealing adhesives such asethylene-vinyl acetate copolymer resin, polyamide resin, polyesterresin, polyethylene resin, ethylene-isobutyl acrylate copolymer resin,butyral resin, polyvinyl acetate and its copolymer resin, cellulosederivatives, polymethyl metacrylate resin, polyvinyl ether resin,polyurethane resin, polycarbonate resin, polypropylene resin, epoxyresin, phenol resin, thermoplastic elastomers such as SBS, SIS, SEBS andSEPS, or reaction hot-melt resins. The adhesive layer has preferably athickness of 4 μm to 20 μm.

[0110] Known volume hologram recording materials such as silver halidematerials, bichromated gelatin emulsions, photo-polymerizable resins,and photo-crosslinking materials may be used for the recording materialin the volume hologram layer 6. For the multilayered volume hologramstructure of the invention, however, it is preferable to use aphotosensitive material employed in dry type volume phase hologramrecording applications, which comprises a matrix polymer, aphoto-polymerizable compound, a photopolymerization initiator and asensitizing dye, because it is excellent in softness.

[0111] The photopolymerizable compounds used herein includephotopolymerizable and photo-crosslinkable monomers, oligomers, andprepolymers having at least one ethylenically unsaturated bond permolecule as will be described later, and their mixtures. For instance,mention is made of unsaturated carboxylic acids and their salts, estersof unsaturated carboxylic acids and aliphatic polyhydric alcoholcompounds, and amide combinations of unsaturated carboxylic acids andaliphatic polyvalent amine compounds.

[0112] Exemplary monomers of the unsaturated carboxylic acids areacrylic acid, methacrylic acid, itaconic acid, crotonic acid,isocrotonic acid, and maleic acid, which may have halogen substituentsas in the case of chlorinated unsaturated carboxylic acids, brominatedunsaturated carboxylic acids, and fluorinated unsaturated carboxylicacids. Exemplary salts of unsaturated carboxylic acids are sodium, andpotassium salts of the aforesaid acids.

[0113] Exemplary monomers for the esters of aliphatic polyhydric alcoholcompounds and unsaturated carboxylic acids are acrylic esters such asethylene glycol diacrylate, triethylene glycol diacrylate,1,3-butanediol diacrylate, tetramethylene glycol diacrylate, propyleneglycol diacrylate, neopentyl glycol diacrylate, trimethylolpropanetriacrylate, trimethylolpropane tri(acryloyloxypropyl) ether,trimethylolethane triacrylate, hexanediol diacrylate,1,4-cyclohexanediol diacrylate, tetraethylene glycol diacrylate,pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritoltetraacrylate, dipentaerythritol diacrylate, dipentaerythritoltriacrylate, dipentaerythritol tetraacrylate, dipentaerythritolhexaacrylate, sorbitol triacrylate, sorbitol tetraacrylate, sorbitolpentaacrylate, sorbitol hexaacrylate, tri(acryloyloxyethyl)isocyanurate, polyester acrylate oligomer, 2-phenoxyethyl acrylate,2-phenoxyethyl methacrylate, phenol ethoxylate monoacrylate,2-(p-chlorophenoxy)ethyl acrylate, p-chlorophenyl acrylate, phenylacrylate, 2-phenylethyl acrylate, (2-acryloxyethyl) ether of bisphenolA, ethoxylated bisphenol A diacrylate, 2-(1-naphthyloxy)ethyl acrylate,o-biphenyl methacrylate, and o-biphenyl acrylate.

[0114] Exemplary monomers for the esters of aliphatic polyhydric alcoholcompounds and unsaturated carboxylic acids are acrylic esters such asethylene glycol diacrylate, triethylene glycol diacrylate,1,3-butanediol diacrylate, tetramethylene glycol diacrylate, propyleneglycol diacrylate, neopentyl glycol diacrylate, trimethylolpropanetriacrylate, trimethylolpropane tri(acryloyloxypropyl) ether,trimethylolethane acrylate, hexanediol diacrylate, 1,4-cyclohexanedioldiacrylate, tetraethylene glycol diacrylate, pentaerythritol diacrylate,pentaerythritol triacrylate, pentaerythritol tetraacrylate,dipentaerythritol diacrylate, dipentaerythritol triacrylate,dipentaerythritol tetraacrylate, dipentaerythritol hexaacrylate,sorbitol triacrylate, sorbitol tetraacrylate, sorbitol pentaacrylate,sorbitol hexaacrylate, tri(acryloyloxyethyl) isocyanurate, and polyesteracrylate oligomer.

[0115] Exemplary methacrylic esters are tetramethylene glycoldimethacrylate, triethylene glycol dimethacrylate, neopentyl -glycoldimethacrylate, trimethylolpropane trimethacrylate, trimethylolethanetrimethacrylate, ethylene glycol dimethacrylate, 1,3-butanedioldimethacrylate, hexanediol dimethacrylate, pentaerythritoldimethacrylate, pentaerythritol trimethacrylate, pentaerythritoltetra-methacrylate, dipentaerythritol dimethacrylate, dipentaerythritolhexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate,bis-[p-(3-methacryloxy-2-hydroxypropoxy)phenyl]dimethylmethane,bis-[p-(acryloxyethoxyphenyl] dimethylmethane,2,2-bis(4-methacryloyloxyphenyl)propane, and methacrylicacid-2-naphthyl.

[0116] Exemplary itoconic esters are ethylene glycol diitaconate,propylene glycol diitaconate, 1,3-butanediol diitaconate, 1,4-butanedioldiitaconate, tetramethylene glycol diitaconate, pentaerythritoldiitaconate, and sorbitol tetraitaconate.

[0117] Exemplary crotonic esters are ethylene glycol dicrotonate,tetramethylene glycol dicrotonate, pentaerythritol dicrotonate, andsorbitol tetracrotonate.

[0118] Exemplary isocrotonic esters are ethylene glycol diisocrotonate,pentaerythritol diisocrotonate, and sorbitol tetraisocrotonate.

[0119] Exemplary maleic esters are ethylene glycol dimaleate,triethylene glycol dimaleate, pentaerythritol dimaleate, and sorbitoltetramaleate.

[0120] Exemplary halogenated unsaturated carboxylic acids are2,2,3,3-tetrafluoropropyl acrylate, 1H,1H,2H,2H-heptadecafluorodecylacrylate, 2,2,3,3-tetrafluoropropylmethacrylate,-1H,1H,2H,2H-heptadecafluorodecyl methacrylate, methacrylicacid-2,4,6-tribromophenyl, dibromoneopentyl dimethacrylate (NK EsterDBN, the trade name of the product made by Shin Nakamura Chemical Co.,Ltd.), dibromopropyl acrylate (NK Ester A-DBP, the trade name of theproduct made by Shin Nakamura Chemical Co., Ltd.), dibromopropylmethacrylate (NK Ester DBP, the trade name of the product made by ShinNakamura Chemical Co., Ltd.), methacrylic acid chloride, methacrylicacid-2,4,6-trichlorophenyl, p-chlorostyrene, methyl-2-chloroacrylate,ethyl-2-chloroacrylate, n-butyl-2-chloroacrylate, tribromophenylacrylate, and tetrabromophenol acrylate.

[0121] Exemplary monomers for the amides of unsaturated carboxylic acidsand aliphatic polyhydric amine-compounds are methylene-bis(acrylamide),methylene-bis(methacrylamide), 1,6-hexamethylene-bis(acrylamide),1,6-hexamethylene-bis(methacrylamide),diethylenetriamine-tris(acrylamide), xylylene-bis(acrylamide),xylylene-bis(methacrylamide), N-phenylmethacrylamide, anddiacetonacrylamide.

[0122] Use may also be made of polyisocyanate compounds having at leasttwo isocyanate groups per molecule as set forth in JP-B 48-41708, andvinyl urethane compounds obtained by the addition of vinyl monomershaving a hydroxyl group and containing at least two polymerizable vinylgroups per molecule, as represented by the following general formula:

CH₂═C(R)COOCH₂CH(R′)OH

[0123] where R and R′ each stands for hydrogen or a methyl group.

[0124] Further, use may be made of urethane acrylates as set forth inJP-A 51-37193, and polyfunctional acrylates and methacrylates such aspolyester acrylates, epoxy resins and (meth)acrylic acids set forth inJP-A 48-64183 and JP-B's 49-43191 and 52-30490.

[0125] Still further, use may be made of photopolymerizable monomers,and oligomers introduced in “Japan Bonding Industry Association”, Vol.20, No. 7, pp. 300 to 308.

[0126] Still further, use may be made of phosphorus-containing monomerssuch as mono(2-acryloyloxyethyl) acid phosphate, (Light Ester PA, thetrade name of the product made by Kyoei-Sha Fats & Oils Chemical Co.,Ltd.) and mono(2-methacryloyl-oxyethyl) acid phosphate (Light Ester Pa.,the trade name of the product made by Kyoei-Sha Fats & Oils ChemicalCo., Ltd.), and epoxy acrylates such as Lipoxy VR-60 (the trade name ofthe product made by Showa Polymer Co., Ltd.) and Lipoxy VR-90 (the tradename of the product made by Showa Polymer Co., Ltd.).

[0127] Still further, use may be made of NK Ester M-230G (the trade nameof the product made by Shin Nakamura Chemical Co., Ltd.), and NK Ester23G (the trade mane of the product made by Shin Nakamura Chemical Co.,Ltd.).

[0128] Still further, use may be made of triacrylates having thefollowing structural formula:

[0129] (Alonix M-315, the trade name of the product made by ToaSynthesis Chemical Co., Ltd., and having the following structuralformula:

[0130] (Alonix M-325, the trade name of the product made by ToaSynthesis Chemical Co., Ltd.). Use may also be made of2,2′-bis(4-acryloxy.diethoxyphenyl)propane (NK Ester A-BPE-4, the tradename of the product made by Shin-Nakamura Chemical Co., Ltd.), andtetramethylolmethane tetraacrylate (NK Ester A-TMMT, the trade name ofthe product made by Shin-Nakamura Chemical Co., Ltd.).

[0131] Exemplary photopolymerization initiators used in initiatorsystems are 1,3-di(t-buthyldioxycarbonyl)benzophenone,3,3′,4,4′-tetrakis(t-buthyldioxycarbonyl)benzophenone, N-phenylglycine,2,4,6-tris(trichloromethyl)-s-triazine, 3-phenyl-5-isooxazolone,2-mercaptobenzimidazole, and imidazole dimers. In view of thestabilization of the recorded hologram, the photopolymerizationinitiator should preferably be decomposed after the recording of thehologram. For instance, an organic peroxide type initiator is easilydecomposed by irradiation with ultraviolet radiation, and so ispreferably used in the practice of the invention.

[0132] Exemplary sensitizing dyes are thiopyrylium salt dyes,merocyanine dyes, quinoline dyes, styrylquinoline dyes, keto-coumarindye, thioxanthene dyes, xanthene dyes, oxonol dyes, cyanine dyes,rhodamine dyes, pyrylium ion dyes, and diphenyliodonium ion dyes, allshowing light absorption at 350 to 600 nm wavelengths. Sensitizing dyesshowing light absorption at wavelength of up to 350 nm, and at least 600nm, too, may be used.

[0133] Examples of the polymer matrix that is a binder resin arepolymethacrylic ester or its partial hydrolyzate, polyvinyl acetate orits hydrolyzate, polyvinyl alcohol or its partially acetalized product,triacetyl cellulose, polyisoprene, polybutadiene, polychloroprene,silicone rubber, polystyrene, polyvinyl butyral, polyvinyl chloride,chlorinated polyethylene, chlorinated polypropylene,poly-N-vinylcarbazole or its derivative, poly-N-vinylpyrrolidone or itsderivative, a copolymer of styrene and maleic anhydride or its halfester, and a copolymer containing at least one polymerization componentselected from the group consisting of copolymerizable monomers such asacrylic acid, acrylic ester, methacrylic acid, methacrylic ester,acrylamide, acrylnitrile, ethylene, propylene, vinyl chloride and vinylacetate, or mixtures thereof. Among these, it is preferable to usepolyisoprene, polybutadiene, polychloroprene, polyvinyl alcohol,polyvinyl acetal that is partially acetalized product of polyvinylalcohol, polyvinyl buryral, polyvinyl acetate, an ethylene-vinyl acetatecopolymer, a vinyl chloride-vinyl acetate copolymer or mixtures thereof.

[0134] The recorded hologram is stabilized at a monomer migration stepby heating. To this end, the matrix polymer has preferably a relativelylow glass transition temperature at which monomer migration takes placereadily.

[0135] The photopolymerizable compound is used in an amount of 10 partsby weight to 1,000 parts by weight, and preferably 10 parts by weight to100 parts by weight per 100 parts by weight of binder resin.

[0136] The photopolymerization initiator is used in an amount of 1 partby weight to 10 parts by weight, and preferably 5 parts by weight to 10parts by weight per 100 parts by weight of binder resin.

[0137] The sensitizing dye is used in an amount of 0.01 part by weightto 1 part by weight, and preferably 0.01 part by weight to 0.5 parts byweight per 100 parts by weight of binder resin.

[0138] Other photosensitive material components, for instance, areplasticizers, glycerin, diethylene glycol, triethylene glycol, variousnonionic surfactants, anionic surfactants, and cationic surfactants.

[0139] The hologram recording material is dissolved in acetone, methylethyl ketone, methyl isobutyl ketone, cyclohexanone, benzene, toluene,xylene, chlorobenzene, tetrahydrofuran, methyl cellosolve, ethylcellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, ethylacetate, 1,4-dioxane, 1,2-dichloroethane, dichloromethane, chloroform,methanol, and isopropanol or a mixed solvent thereof to form a coatingsolution having a solids content of 15% to 25%.

[0140] For such a coating solution, for instance, Omnidex 352 andOmnidex 706, Du Pont, are used.

[0141] The hologram recording layer has a thickness of 0.1 μm to 50 μm,and preferably 5 μm to 20 μm.

[0142] Before the hologram recording layer is built in the multilayeredvolume hologram structure, it is coated on a provisional substrate at apost-drying thickness of 1 μm to 100 μm, and preferably 4 μm to 20 μm.Used for the provisional substrate are a glass plate, an acrylic plate,a polycarbonate plate, a polyethylene plate, a polypropylene plate, apolyethylene terephthalate plate, and a polystyrene plate, all having athickness of 0.01 mm to 100 mm, and preferably 1 mm to 5 mm. Amongthese, it is preferable to use the glass, acrylic, and polycarbonateplate because they have sufficient mechanical strength, a low index ofdouble refraction, and high transparency. For the provisional plate, afilm previously coated with a photosensitive material may also be used.

[0143] A protective layer is provided on the hologram recording layer.The protective layer may be formed by laminating together transparentresin films that are of good weather resistance and have a thickness of0.001 mm to 10 mm, and preferably 0.01 mm to 0.1 mm, typicallypolyethylene terephthalate films, polyethylene films, polypropylenefilms, polyvinyl chloride films, acrylic films, polyacetyl cellulosefilms, and cellulose acetate butyrate films, using rubber rollers.Alternatively, the protective layer may be formed by the spin coating offilm forming materials such as triacetyl cellulose, polyvinyl alcohol,and polymethyl methacrylate.

[0144] As is the case with a conventional dry hologram-making process, ahologram is recorded in the volume hologram layer by steps of recordinginterference fringes in the hologram recording layer, using two-beamlaser light such as argon light, and laser light (of 514.5 nmwavelength) with a Lippmann type hologram making system, decomposing aphoto-polymerization initiator by irradiation with ultraviolet radiationof 0.1 mJ/cm² to 10,000 mJ/cm², and preferably 10 mJ/cm² to 1,000 mJ/cm²from a light source such as an ultra high pressure mercury-vapor lamp, ahigh pressure mercury-vapor lamp, a carbon arc lamp, a xenon arc lamp,and a metal halide lamp, and thermally treating a photopolymerizablecompound (e.g., at 120° C. for 120 minutes) for diffusion and migration,so that a stable hologram can be formed.

[0145] To record the hologram in the hologram recording layer, theaforesaid volume hologram recording material is coated on a substratefilm, so that interference fringes corresponding to the wavefront oflight from an object is recorded in the layer in the form oftransmittance modulation or refractive index modulation. Alternatively,while an original volume hologram plate is in close contact with thehologram recording layer, the hologram recording layer is exposed tolight and developed, so that the volume hologram is replicated andthereby recorded therein.

[0146] The hologram is preferably free of surface asperities, and so itis preferable to use a reflection type volume hologram (Lippmannhologram) or a transmission type volume hologram.

[0147] A Lippmann hologram is here explained. The Lippmann hologram isrecorded using such an arrangement as shown in FIG. 37(a), andreconstructed on such principles as illustrated in FIG. 37(b). Morespecifically, coherent object light 111 bearing information about theobject O to be recorded-is incident on one side of a hologramphotosensitive material 110 and, at the same time, coherent referencelight 112 of the same wavelength is incident on the opposite side of thematerial 110 at a given angle of incidence. There-upon, the object light111 and the reference light 112 interfere with each other in thehologram photosensitive material 110, so that the Lippmann hologram (avolume type hologram interference fringes) is recorded therein. Toreconstruct this hologram, one side of a material 120 with the Lippmannhologram recorded therein (the hologram photosensitive material 110) isirradiated with reconstructing illumination light 122 from the samedirection as that of the reference light 112 used for recording thehologram. Thereupon, the incident light is diffracted by the recordedvolume type hologram interference fringes. The diffracted light 123 isdiffracted in the same direction as that of the light emitted from theposition of the object O to be recorded, so that an image O′ isreconstructed at the original position of the object O. Alternatively,the opposite side of the material 120 is irradiated with thereconstructing illumination light 122 propagating in an oppositedirection to the reference light 112 used for recording the hologram, sothat the image O′ is reconstructed at the original position of theobject O. In either case, the Lippmann hologram can reconstruct an imageof a three-dimensional object recorded therein or a two-dimensionalpattern recorded therein in a given space.

[0148] Such a Lippmann hologram has some characteristic features ofbeing capable of reconstructing the recorded image by ambient light suchas indoor illumination light, recording and reconstructing athree-dimensional object and recording an object in a multiple manner,and having wave-length selectivity and angle selectivity.

[0149] When the Lippmann hologram is used, therefore, the patternrecorded therein can be observed by illumination light as a specificcolored pattern existing in the air.

[0150] Then, a transmission type volume hologram is explained. Thetransmission type volume hologram is recorded using such an arrangementas shown in FIG. 38(a), and reconstructed on such principles asillustrated in FIG. 38(b). An image is recorded by striking coherentobject light 131 bearing information about the object O to be recordedon one side of a hologram photosensitive material 130 of some thicknessand, at the same time, striking coherent reference light 132 of the samewavelength on the same side of the material 130 at a given angle ofincidence, so that the object light 131 and the reference light 132interfere with each other in the material 130 to record a volume type ofhologram interference fringes therein.

[0151] For hologram reconstruction, a material 140 with the imagerecorded therein (the hologram photosensitive material 130) isirradiated with reconstructing illumination light 132 from the samedirection as that of the reference light 132 used for recording theimage. Thereupon, the incident light is diffracted by the recordedvolume type hologram interference fringes. The diffracted light 133 isdiffracted in the same direction as that of the light emitted from theposition of the object O to be recorded, so that an image O′ isreconstructed at the original position of the object O. Alternatively,the opposite side of the material 140 is irradiated with thereconstructing illumination light 132 propagating in an oppositedirection to the reference light 132 used for recording the hologram, sothat the image O′ is reconstructed at the original position of theobject O.

[0152] In the invention, it is acceptable to use a reflection typehologram obtained by evaporating a reflecting layer on the back side ofthe transmission type volume hologram.

[0153] The surface protective film 7, for instance, may be formed ofpolyethylene, polypropylene, polyethylene fluoride, polyvinylidenefluoride, polyvinyl chloride, polyvinylidene chloride, ethylene-vinylalcohol, polyvinyl alcohol, polymethyl methacrylate, polyether sulfone,polyether ketone, polyamide, tetrafluoroethylene-perfluoroalkylvinylether copolymers, polyethylene terephthalate, and polyimide, and has athickness of 2 μm to 200 μm, and preferable 10 μm to 50 μm.

[0154] Although not illustrated, it is preferable that the surfaceprotective film 7 is subjected thereon with a hard coat treatment, ifrequired, for the purpose of improving the surface protective propertiesof the surface protective film 7. The hard coat treatment is preferablycarried out by the dipping, spray, and roll coating of materials basedon silicone, fluorine-containing silicone, melamine alkyd, and urethaneacrylate (of the ultraviolet radiation curing type), thereby obtaining apost-drying film thickness of 1 μm to 50 μm, and preferably 3 μm to 25μm.

[0155] Although not illustrated, the surface of the surface protectivefilm 7 or the surface of the hard coat film is preferably subjected to areleasing treatment for the purpose of prevent any intentional releasethereof. The surface protective film or the hard coat film thereof mayotherwise be released by pasting a high rigidity film thereon andpeeling off it. For this purpose, release agents such as fluorinerelease agents, silicone release agents, stearate release agents, andwax release agents may be provided by suitable coating techniques suchas dipping coating, spray coating, and roll coating.

[0156] Although again not illustrated, the surface or hard coat treatedsurface of the surface protective film 7 is preferably subjected to arelease treatment for the purpose of preventing a release thereof bypeeling a high rigidity film applied thereon, thereby preventingfalsification. The release treatment may be carried out by the dippingcoating, spray coating, and roll coating of a fluorine release agent, asilicone release agent, a stearate release agent, and a wax releaseagent.

[0157] Preferably, the adhesive layers, volume hologram layer andsurface protective film should be all transparent.

[0158] The object of the first multilayered volume hologram structure ofthe invention that has such a multilayer structure as mentioned above isto certainly break the volume hologram layer, for instance, upon anintentional release of the surface protective film, thereby ensuringprevention of falsification such as a photograph replacement.

[0159] When the peeling strength between the surface protective film 7and the volume hologram layer 6 is weak, the volume hologram layer isexposed upon a release of the surface protective film 7. Since thevolume hologram layer 6 is composed of acrylic resin or gelatin and sois brittle, it can break down immediately after the photograph isstripped off, thereby achieving reliable prevention of falsification. Ifthis peeling strength should be strong, however, the volume hologramlayer would be released following the release of the surface protectivefilm.

[0160] When the surface protective film contains a plasticizer, a secondadhesive layer 5″ is interleaved between the surface protective film 7and the volume hologram layer 6 as shown in FIG. 3, thereby preventingthe migration of the plasticizer from having any influence on thehologram recorded in the volume hologram layer. If the adhesive strengthof the second adhesive layer 5″ should be stronger than that of thefirst adhesive layer 5′, however, the volume hologram layer would bereleased following a release of the surface protective film, asmentioned just above.

[0161] To achieve the aforesaid object, the peeling strength, with whichthe multilayer structure comprising first adhesive layer 5′/volumehologram layer 6/surface protective layer 7 as shown in FIG. 2 or themultilayer structure comprising first adhesive layer 5′/volume hologramlayer 6/second adhesive layer 5 ′/surface protective layer 7 as shown inFIG. 3 is released from the associated substrate 2, should be greaterthan the breaking strength or tensile strength at 1% elongation of eachmultilayer structure. In the present disclosure, each multilayerstructure will be called the multilayer structure to be released.

[0162] The peeling strength (Kg/25 mm) with which the multilayerstructure is released from the substrate is determined by the 180°peeling test according to JIS Z0237 (using a tensile compression testingmachine, e.g., model SV-201-E made by Konno Seisakusho Co., Ltd.) underthe following measuring conditions: Measuring atmosphere: 25° C. × RH50% Test piece: 25 mm width Rate of pulling: 200 mm/min.

[0163] In the invention, it is preferable that the peeling strength ofthe multilayer structure is in the range of 0.1 Kg/25 mm to 5.0 Kg/25mm, and especially 1 Kg/25 mm to 3 Kg/25 mm. A multilayer structurehaving a peeling strength of lower than 0.1 Kg/25 mm is practicallyunacceptable, because it is too brittle to be laminated on a photographin view of its breaking strength, as will be described later. The upperlimit of 5.0 Kg/25 mm is determined by an upper limit on the adhesiveforce of the adhesive agent having re-bondability.

[0164] When the multilayer structure is released from the substrate, itis required that the multilayer structure break down or show anelongation of at least 1%. The breaking strength or tensile strength at1% elongation of the multilayer structure to be released is measuredaccording to JIS K7127-1989, using a tensile compression testingmachine, e.g., model SV-201-E made by Konno Seisakusho Co., Ltd. underthe following measuring conditions: Measuring atmosphere: 20° C. × 65%RH Test piece: 25 mm width Lamination: Press lamination by onereciprocation of rubber roller Lamination time: 60 minutes afterlamination Peel angle: 180° Peeling rate: 250 mm/min.

[0165] In the first multilayered volume hologram structure of theinvention, the breaking strength or tensile strength at 1% elongation ofthe multilayer structure to be released is in the range of 0.01 Kg/mm²to 5 Kg/mm², and preferably 0.03 Kg/mm² to 3 Kg/mm², as can be seen fromFIG. 4 wherein the breakdown of the multilayer structure is indicated byan arrow, and as can be seen from FIG. 5 wherein how the multilayerstructure is elongated is indicated by an arrow. When the breakingstrength or tensile strength at 1% elongation is below 0.01 Kg/mm², themultilayer structure to be released is too brittle to be laminated on aphotograph. When the upper limit of 5.0 Kg/mm² is exceeded, on the otherhand, it is impossible to achieve a complete breakdown of the volumehologram layer because the volume hologram layer follows a release ofthe surface protective film.

[0166] In the first multilayered volume hologram structure of theinvention, it is essentially required that the peeling strength, withwhich the multilayer structure comprising a volume hologram layer and asurface protective film is released from the substrate, be in the rangeof 0.1 Kg/25 mm to 5.0 Kg/25 mm, the breaking strength or tensilestrength at 1% elongation of the multilayer structure be in the range of0.01 Kg/mm² to 5.0 Kg/mm², and the peeling strength, with which themultilayer structure comprising a volume hologram layer and a surfaceprotective film is released from the substrate, be greater than thebreaking strength or tensile strength at 1% elongation of the multilayerstructure comprising a volume hologram layer and a surface protectivefilm. This ensures a complete breakdown or an at least 1% elongation ofthe multilayer structure comprising a volume hologram layer and asurface protective film upon a release of the multilayer structure fromthe substrate, so that a complete breakdown of the recorded hologram isachievable. In the invention, either one of the breaking strength ortensile strength at 1% elongation of the multilayer structure to bereleased may be in the aforesaid range.

[0167] It is here to be noted that both the adhesive layer and volumehologram layer in the multilayer structure are very soft, and so thebreaking strength or tensile strength at 1% elongation of the multilayerstructure depends on the breaking strength or tensile strength at 1%elongation of the surface protective film 7. When the multilayerstructure is designed, therefore, it is preferable to take the breakingstrength or tensile strength at 1% elongation of the surface protectivefilm into consideration.

[0168] For the surface protective film 7, for instance, any one ofpolyethylene film (PE), polypropylene film (PP), ethylene-vinyl alcoholcopolymer film (EVOH), polyvinyl alcohol film (PVA), polymethylmethacrylate film (PMMA), polyether sulfone film (PES), polyamide film(nylon film), and tetrafluoroethylene-perfluoroalkylvinyl ethercopolymer film (PFA) is preferably selected from the surface protectivefilms already mentioned while care is taken of peeling strength. It isthus possible to impart preferable breaking strength or tensile strengthat 1% elongation to the multilayer structure to be released.

[0169] For reference, the breaking strength (Kg/mm²) and tensilestrength at 1% elongation (Kg/mm²) of these plastic films are shown inTable 1 given below. However, it is to be noted that these values varyslightly depending on the degree of elongation. If required, consultgenerally available data. In Table 1, MD and TD are values as measuredin the lengthwise and widthwise directions of film, respectively. Thebreaking strength and tensile strength at 1% elongation of polyimidefilm (PI), polyethylene terephthalate film (PET) and polyether etherketone film (PEEK) are also shown in Table 1. TABLE 1 Tensile StrengthBreaking Strength at 1% Elongation PE MD:2.14 TD: 2.05 — PP MD: 5.0 TD:2.5 MD: 0.65 TD: 0.5 EVOH MD: 9.0 TD: 4.0 MD: 2.2 TD: 2.2 PVA MD: 5.5TD: 5.5 MD: 0.25 TD: 0.25 PMMA 3.0 1.2 PES 8.5 2.2 Nylon MD: 22 TD: 28MD: 1.6 TD: 1.1 PFA MD: 4.0 TD: 3.5 MD: 0.49 TD: 0.47 PI 17.6 3.0 PETMD: 20 TD: 22 MD: 4.0 TD: 4.1 PEEK 13 3.0

[0170] One exemplary layer structure in section of the label used forthe fabrication of the first multilayered volume hologram structure ofthe invention is explained with reference to FIGS. 6(a) and 6(b).

[0171] In the drawings, 10 represents a multilayered volume hologramstructure-making label, and 11 stands for a release paper. The samenumerals as in FIGS. 2 and 3 indicate the same parts.

[0172] The label 10 shown in FIG. 6(a) is a label for the fabrication ofthe first multilayered volume hologram structure, which comprises afirst adhesive layer 5′, a volume hologram layer 6 and a surfaceprotective film 7 laminated on the release paper 11 in the describedorder.

[0173] For the release paper 11, not only ordinary release paper butalso a releasable film obtained by the release treatment of the surfaceof a polyethylene terephthalate film with a fluorine or silicone releaseagent may be used. Preferably but not exclusively, the back surface ofthe release paper that does not oppose to the adhesive layer issubjected to a release treatment to avoid blocking due to a portion ofthe adhesive agent forced out of the side of the label. To release amultilayer structure of suitable size from the release paper, therelease paper may be subjected to so-called “half die cutting” at onlyan area with the multilayer structure laminated thereon. Alternatively,it is acceptable to provide perforations or other cuts in the releasepaper.

[0174] Upon removal of the release paper 11, the exposed first adhesivelayer 5′ of the label 10 is put on a substrate 2 with a photograph, etc.pasted thereon, so that a multilayered volume hologram structure asshown in FIG. 2 can be fabricated.

[0175] The label shown in FIG. 6(b) comprises a first adhesive layer 5′,a volume hologram layer 6, a second adhesive layer 5′ and a surfaceprotective layer 7 laminated on the release paper 11 in the describedorder. As in FIG. 6(a), the release paper 11 is removed from the label10 to put the exposed first adhesive layer 5′ of the label 10 on asubstrate 2 with a photograph, etc. pasted thereon, so that amultilayered volume hologram structure as shown in FIG. 3 can befabricated.

[0176] Thus, the label for the fabrication of the first multilayeredvolume hologram structure is useful for the fabrication of the firstmultilayered volume hologram structure.

[0177] In what follows, the first multilayered volume hologram structureof the invention and the label for making the same will be explainedwith reference to illustrative examples 1 to 3, and comparative example1.

ILLUSTRATIVE EXAMPLE 1 Preparation of Hologram-Recorded Material

[0178] A Lippmann hologram was recorded on a hologram recording mediumobtained by laminating a hologram recording material layer (a 20 μmthick Omnidex 706 made by Du Pont) and a polyvinyl chloride film on apolyethylene terephthalate film in the described order.

Preparation of Silicone Separator/Adhesive Layer

[0179] An adhesive agent (Nissetsu PE-118 made by Nippon Carbide Co.,Ltd.) was coated on a silicone separator (a 50 μm thick SP-PET made byTokyo Cellophane Paper Co., Ltd.) at a dry thickness of 10 μm.

Preparation of Surface Protective Film/Adhesive Layer/Silicone Separator

[0180] An adhesive agent (Nissetsu PE-118 made by Nippon Carbide Co.,Ltd.) was coated on a silicone separator (a 50 μm thick SP-PET made byTokyo Cellophane Paper Co., Ltd.) at a dry thickness of 10 μm, and anon-stretched ethylene-vinyl alcohol copolymer film (a 12 μm thick EvalEF-F made by Kuraray Co., Ltd.) was then laminated on the surface of theadhesive layer.

[0181] The surface of the ethylene-vinyl alcohol copolymer film wasspray coated with a fluorine release agent (Mold Spat K681 made by AsahiGlass Co., Ltd.) for release treatment.

Preparation of Multilayered Volume Hologram Structure-Making Label

[0182] The polyvinyl chloride film was removed from the aforesaidhologram recording material, and the aforesaid siliconeseparator/adhesive layer was laminated on the hologram recordingmaterial to obtain a PET film/hologram layer/adhesive layer/siliconeseparator multilayered structure.

[0183] The PET film was removed from this multilayered structure whilethe silicone separator was removed from the aforesaid surface protectivelayer/adhesive layer/silicone separator structure. Then, lamination wascarried out to obtain a label for the fabrication of the multilayeredvolume hologram structure of the invention, which comprised a surfaceprotective film/adhesive layer/hologram layer/adhesive layer/siliconeseparator structure.

[0184] The breaking strength of this label from which the siliconeseparator was removed was found to be MD=10 Kg/mm² and TD=5.2 Kg/mm² asmeasured according to JIS K7127-1989.

[0185] For reference, the breaking strength of the non-stretchedethylene-vinyl alcohol copolymer film (a 12 μm thick Eval EF-F made byKuraray Co., Ltd.) used as the surface protective film was MD=8.7 Kg/mm²and TD=4.1 Kg/mm², as similarly measured.

Preparation of Multilayered Volume Hologram Structure

[0186] The label, from which the silicone separator was removed, waslaminated at the adhesive layer on a photograph and informationarea-bearing substrate. After the obtained multilayered structure waspermitted to stand alone for 24 hours, a surface protective film/volumehologram layer structure was forcibly removed from the multilayeredstructure. However, it was found that the surface protective filmfractured with a breakdown of the volume hologram layer.

Measurement of Peeling Strength

[0187] A label for the fabrication of the multilayered volume hologramstructure was prepared as in illustrative example 1 with the exceptionthat the following structure was used instead of the aforesaid surfaceprotective film/adhesive layer/silicone separator structure. That is, anadhesive agent (Nissetsu PE-118 made by Nippon Carbide Co., Ltd.) wascoated on a silicone separator (a 50 μm thick SP-PET made by TokyoCellophane Paper Co., Ltd.) at a dry thickness of 10 μm, and an easilybondable polyester film (a 50 μm thick HP-7 made by Teijin Limited) waslaminated on the surface of the adhesive agent layer. As in illustrativeexample 1, release treatment was applied to the surface of thispolyester film.

[0188] This label, from which the silicone separator was removed, waslaminated on a photograph and information area-bearing substrate, andallowed to stand alone for 24 hours. The peeling strength of themultilayered structure was found to be 3.1 Kg/25 mm, as measured by the180° peeling test according to JIS Z0237. It is here to be noted thatthe volume hologram layer peeled off following the PET film.

ILLUSTRATIVE EXAMPLE 2

[0189] A label for the fabrication of the multilayered volume hologramstructure was prepared as in illustrative example 1 with the exceptionthat the following structure was used instead of the aforesaid surfaceprotective film/adhesive layer/silicone separator structure. That is, anadhesive agent (Nissetsu KP-981 made by Nippon Carbide Co., Ltd.) wascoated on a silicone separator (a 50 μm thick SP-PET made by TokyoCellophane Paper Co., Ltd.) at a dry thickness of 10 μm, and anon-stretched polypropylene film (a 50 μm thick Torcero CP-SC made byTokyo Cellophane Paper Co., Ltd.) was laminated on the surface of theadhesive layer. As in illustrative example 1, release treatment wasapplied to the surface of this polypropylene film.

[0190] The tensile strength at 1% elongation of the label, from whichthe silicone separator was removed, was found to be MD=0.78 Kg/mm², asmeasured according to JIS K7127-1989. For reference, the tensilestrength at 1% elongation of the non-stretched polypropylene film (a 50μm thick Torcero CP-SC made by Tokyo Cellophane Paper Co., Ltd.) used asthe surface protective film was 0.11 Kg/mm², as similarly measured.

Preparation of Multilayered Volume Hologram Structure

[0191] The label, from which the silicone separator was removed, waslaminated at the adhesive layer on a photograph and informationarea-bearing substrate. After the obtained multilayered structure waspermitted to stand alone for 24 hours, a surface protective film/volumehologram layer structure was forcibly removed from the multilayeredstructure. However, it was found that the surface protective filmelongated with an elongation of the volume hologram layer; it wasabsolutely impossible to achieve hologram reconstruction.

ILLUSTRATIVE EXAMPLE 3

[0192] A label for the fabrication of the multilayered volume hologramstructure was prepared as in illustrative example 1 with the exceptionthat the following structure was used instead of the aforesaid surfaceprotective film/adhesive layer/silicone separator structure. That is, anadhesive agent (Nissetsu KP-981 made by Nippon Carbide Co., Ltd.) wascoated on a silicone separator (a 50 μm thick SP-PET made by TokyoCellophane Paper Co., Ltd.) at a dry thickness of 10 μm, and an extrudedpolyvinyl chloride film (a 50 μm thick film made by Riken VinylIndustries Co., Ltd.) was laminated on the surface of the adhesivelayer. As in illustrative example 1, release treatment was applied tothe surface of this polyvinyl chloride film.

[0193] The tensile strength at 1% elongation of the label, from whichthe silicone separator was removed, was found to be MD=0.11 Kg/mm², asmeasured according to JIS K7127-1989. For reference, the tensilestrength at 1% elongation of the extruded polyvinyl chloride film (a 50μm thick film made by Riken Vinyl Industries Co., Ltd.) used as thesurface protective film was 0.03 Kg/mm², as similarly measured.

Preparation of Multilayered Volume Hologram Structure

[0194] The label, from which the silicone separator was removed, waslaminated at the adhesive layer on a photograph and informationarea-bearing substrate. After the obtained multilayered structure waspermitted to stand alone for 24 hours, a surface protective film/volumehologram layer structure was forcibly removed from the multilayeredstructure. However, it was found that the surface protective filmelongated with an elongation of the volume hologram layer; it wasabsolutely impossible to achieve hologram reconstruction.

COMPARATIVE EXAMPLE 1

[0195] A label for the fabrication of the multilayered volume hologramstructure was prepared as in illustrative example 1 with the exceptionthat the following structure was used instead of the aforesaid surfaceprotective film/adhesive layer/silicone separator structure. That is, anadhesive agent (Nissetsu PE-118 made by Nippon Carbide Co., Ltd.) wascoated on a silicone separator (a 50 μm thick SP-PET made by TokyoCellophane Paper Co., Ltd.) at a dry thickness of 10 μm, and an easilybondable polyester film (a 50 μm thick HP-7 made by Teijin Limited) waslaminated on the surface of the adhesive agent layer. As in illustrativeexample 1, release treatment was applied to the surface of thispolyester film.

[0196] The breaking strength of the label, from which the siliconeseparator was removed, was found to be 21.9 Kg/mm², as measuredaccording to JIS K7127-1989. For reference, the breaking strength of thebondable polyester film (a 50 μm thick HP-7 made by Teijin Limited) usedas the surface protective film was 21 Kg/mm², as measured in a similarmanner.

Preparation of Multilayered Volume Hologram Structure

[0197] The label, from which the silicone separator was removed, waslaminated at the adhesive layer on a photograph and informationarea-bearing substrate. After the obtained multilayered structure waspermitted to stand alone for 24 hours, the surface protectivefilm/volume hologram layer structure was forcibly stripped from themultilayered structure. The multilayer structure could barely bereleased from the latter although it was difficult to release the formerfrom the adhesive layer interface due to the rigidity of the surfaceprotective film. However, there was no significant damage to thehologram layer.

[0198] Then, the second multilayered volume hologram structure of theinvention and the label for making the same are explained.

[0199] The second multilayered volume hologram structure of theinvention is explained with reference to FIG. 1 that is a front view ofthe first multilayered volume hologram structure of the invention. It ishere to be noted that FIG. 7 is a sectional view of the secondmultilayered volume hologram structure as taken along the A-A line inFIG. 1, and FIG. 8 is a sectional view illustrative of anotherembodiment of the second multilayered volume hologram structure.

[0200] In FIGS. 7 and 8, a third adhesive layer and a colored sheet areindicated at 5 and 9, respectively, and other reference numerals havethe same meanings as mentioned in conjunction with the firstmultilayered volume hologram structure of the invention.

[0201] What is explained in conjunction with FIG. 1 is the same asexplained in conjunction with the first multilayered volume hologramstructure of the invention.

[0202] As shown in FIG. 7, the second multilayered volume hologramstructure comprises a substrate 2 and a photograph of face orinformation area 4 pasted on the substrate 2 with a photographic paste3. A first adhesive layer 5′, a volume hologram layer 6, a secondadhesive layer 5″ and a surface protective film 7 are laminated on thesubstrate 2 and astride the photograph of face 4 in the described order.

[0203] The substrate 2, photographic paste 3, photograph of face orinformation area 4, volume hologram layer 6 and surface protective film7 are the same as those used with the first multilayered volume hologramstructure of the invention.

[0204] For the first adhesive layer 5′ in the second multi-layeredvolume hologram structure of the invention, for instance, use may bemade of acrylic resin, acrylic ester resin, and vinyl acetate resin ortheir copolymers as well as styrene-butadiene copolymer, natural rubber,casein, gelatin, rosin ester, terpene resin, phenolic resin, styreneresin, coumarone-indene resin, polyvinyl ether, and silicone resin. Theadhesive layer 5′ may also be formed of adhesives based onα-cyanoacrylate, silicone, maleimide, styrol, polyolefin, resorcinol,and polyvinyl ether as well as heat seating adhesives such asethylene-vinyl acetate copolymer resin, polyamide resin, polyesterresin, polyethylene resin, ethylene-isobutyl acrylate copolymer resin,butyral resin, polyvinyl acetate and its copolymer resin, cellulosederivatives, polymethyl methacrylate resin, polyvinyl ether resin,polyurethane resin, polycarbonate resin, polypropylene resin, epoxyresin, phenol resin, thermoplastic elastomers such as SBS, SIS, SEBS andSEPS, or reaction hot-melt resins.

[0205] The second adhesive layer 5″, for instance, may again be formedof acrylic resin, and acrylic ester resin or their copolymers as well asstyrene-butadiene copolymer, natural rubber, casein, gelatin, rosinester, terpene resin, phenolic resin, styrene resin, coumarone-indeneresin, polyvinyl ether, and silicone resin. The adhesive layer 5″ mayalso be formed of adhesives based on α-cyanoacrylate, silicone,maleimide, styrol, polyolefin, resorcinol, and polyvinyl ether.

[0206] Each adhesive layer may be formed by coating and have a thicknessof 4 μm to 20 μm.

[0207] The second multilayered volume hologram structure of theinvention is characterized in that the adhesion of the second adhesivelayer 5″ is weaker than the adhesion of the first adhesive layer 5′ sothat the surface protective film 7 can be released from the volumehologram layer 6 upon delamination thereof. To make the adhesion of thesecond adhesive layer 5″ weaker than the adhesion of the first adhesivelayer 5′, a sensible selection may be made from materials that form thefirst adhesive layer and materials that form the second adhesive layer.

[0208] The adhesion used herein may be given by the peeling strength(Kg/25 mm) of the multilayer structure, and estimated by the 180°peeling test according to JIS Z0237 (using a tensile compression testingmachine, e.g., model SV-201-E manufactured by Konno Seisakusho Co.,Ltd.). The measuring conditions are the same as mentioned in conjunctionwith the first multilayered volume hologram structure of the invention.

[0209] The adhesion of the second adhesive layer 5′ may be estimated bythe peeling strength with which the surface protective film 7 isreleased from the multilayer structure, and may be in the range of 0.001Kg/25 mm to 0.1 Kg/25 mm, and preferably 0.01 Kg/25 mm to 0.1 Kg/25 mm.The adhesion of the first adhesive layer 5′ is stronger than theadhesion of the second adhesive layer 5″, and may be estimated by thepeeling strength with which the volume hologram layer 6 is released fromthe substrate 2 or photograph 4. The peeling strength may be in therange of 0.1 Kg/25 mm to 5.0 Kg/25 mm, and preferably 0.5 Kg/25 mm to3.0 Kg/25 mm.

[0210] When the adhesion of the second adhesive layer 5′ is weaker thanthe adhesion of the first adhesive layer 5′, the volume hologram layer 6is undulated at a constant interval following a release of the surfaceprotective film 7 therefrom, as shown at p in a schematic representationof FIG. 9(a) with no adhesive layers illustrated. In this case, as shownin a perspective representation of FIG. 9(b), releasing lines q orso-called chatter marks are formed on the volume hologram layer 6 at aconstant interval in a direction perpendicular to a releasing directionX.

[0211] The second multilayered volume hologram structure of theinvention makes use of this phenomenon to prevent falsification. Whenthe hologram recorded in the volume hologram is copied after a releaseof the surface protective film, the releasing lines are copied at thesame time. It is thus possible to tell whether the copy is genuine orspurious. This is also true of when the hologram layer with thereleasing lines formed thereon is pasted on another substrate; it ispossible to tell whether the hologram layer is genuine or spurious dueto the presence of the releasing lines.

[0212] Another embodiment of the second multilayered volume hologramstructure of the invention is explained with reference to FIG. 8 whereina colored sheet and a third adhesive layer are indicated at 9 and 5,respectively, and the same numerals as in FIG. 7 indicates the sameparts.

[0213] As shown in FIG. 8, the second embodiment of the secondmultilayered volume hologram structure of the invention comprises acolored sheet laminated on a substrate with a third adhesive layer 5interleaved therebetween. A first adhesive layer 5′, a volume hologramlayer 6, a second adhesive layer 5″ and a surface protective film 7 arelaminated on the colored sheet in the described order.

[0214] For the colored sheet 9, for instance, use may be made of apolyester, triacetyl cellulose, polypropylene or acrylic film coloredwith a dye or pigment having no adverse influence on the volume hologramlayer. When it is required to see a photograph 4 or the like through thecolored sheet, a transparent colored sheet may be used, and when it isnot required, an opaque colored sheet may be used. The colored sheet mayhave a thickness of 10 μm to 100 μm. If the colored sheet 9 having acolor different from or in complementary relation to the color of thehologram or a black color is interleaved in the multilayered structure,it is then possible to enhance the contrast of a hologram image.

[0215] The third adhesive layer 5 may be formed of the same material forthe first adhesive layer, and have an adhesion equivalent to that of thefirst adhesive layer 5′.

[0216] In this embodiment, it is preferable that the first and secondadhesive layers, volume hologram layer and surface protective film areall transparent.

[0217] A label for making the second multilayered volume hologramstructure of the invention is explained with reference to FIGS. 10(a)and 10(b) that are sectional views thereof.

[0218] In FIGS. 10(a) and 10(b), a label for making the multilayeredvolume hologram structure and a release paper are indicated at 20 and11, respectively. The same numerals as in FIGS. 7 and 8 indicate thesame parts.

[0219] A label 20 of FIG. 10(a) comprises a first adhesive layer 5′, avolume hologram layer 6, a second adhesive layer 5″ and a surfaceprotective layer 7 laminated on the release paper 11 in the describedorder.

[0220] For the release paper 11, use may be made of the same releasepaper as mentioned in conjunction with the label for making the firstmultilayered volume hologram structure of the invention. The label, fromwhich the release paper is removed, is laminated at the first adhesivelayer 5′ on a substrate 2 with a photograph or the like pasted thereon,so that the multilayered volume hologram structure shown in FIG. 7 canbe fabricated.

[0221] A label 20 of FIG. 10(b) comprises a third adhesive layer 5, acolored sheet 9, a first adhesive layer 5′, a volume hologram layer 6, asecond adhesive layer 5″ and a surface protective film 7 laminated onthe release paper 11 in the described order.

[0222] To laminate the label 20 on a substrate 2 such as a certificateor credit card, the label 20, from which the release paper is removed,is laminated at the third adhesive layer 5 on the substrate 2, so thatthe multilayered volume hologram structure shown in FIG. 8 can beobtained.

[0223] In what follows, the second multilayered volume hologramstructure of the invention and the label for making the same will beexplained with reference to illustrative examples 4 and 5.

ILLUSTRATIVE EXAMPLE 4 Preparation of Hologram-Recorded Material

[0224] A Lippmann hologram was recorded on a hologram recording mediumobtained by laminating a hologram recording material layer (a 20 μmthick Omnidex 706 made by Du Pont) and a polyvinyl chloride film on apolyethylene terephthalate film in the described order.

Preparation of Silicone Separator/First Adhesive Layer 5′

[0225] An adhesive agent (Nissetsu PE-118 made by Nippon Carbide Co.,Ltd.) was coated by die coating on a silicone separator (a 50 μm thickSP-PET made by Tokyo Cellophane Paper Co., Ltd.) at a dry thickness of20 μm.

Surface Protective Film/Second Adhesive Layer 5″/Silicone Separator

[0226] A PET/acrylic adhesive layer/silicone separator (Sanitechto H225Emade by Sanei Kaken Co., Ltd.) structure was provided.

Preparation of Label for Multilayered Volume Hologram Structure-MakingLabel

[0227] The polyvinyl chloride film was removed from thehologram-recorded material, and the aforesaid silicone separator/firstadhesive layer 5′ was laminated on the hologram-recorded material toobtain a PET film/hologram layer/silicone separator multilayerstructure.

[0228] The PET film was removed from this multilayer structure while thesilicone separator was removed from the aforesaid surface protectivelayer/second adhesive layer 5″/silicone separator structure. Then,lamination was carried out to obtain a label for the fabrication of themultilayered volume hologram structure of the invention, which compriseda surface protective film/second adhesive layer 5″/hologram layer6/first adhesive layer 5′/silicone separator structure, and is shown inFIG. 10(a).

Preparation of Multilayered Volume Hologram Structure

[0229] The label, from which the silicone separator was removed, waslaminated at the first adhesive layer 5′ on a paper substrate with aphotograph pasted thereon, as shown in FIG. 7.

[0230] After this multilayered volume hologram structure was allowed tostand alone for 24 hours, the surface protective film 7 was strippedtherefrom.

[0231]FIG. 11 is a graphical representation illustrative of the state ofa peeling strength change upon a release of the surface protective filmfrom the multilayered volume hologram structure. The state shown at (a)in FIG. 11 corresponds to areas with releasing lines formed at intervalsof 2 to 4 mm. Even after the surface protective film was re-laminated atthe original position, the releasing lines were clearly visible.

ILLUSTRATIVE EXAMPLE 5

[0232] The second multilayered volume hologram structure and a label formaking the same were prepared as in illustrative example 4 with theexception that the following silicone separator/third adhesive layer5/colored sheet/first adhesive layer 5′ structure was used in place ofthe silicone separator/first adhesive layer 5′ used for the fabricationof the aforesaid multilayered volume hologram structure-making label.

Preparation of Silicone Separator/Third Adhesive Layer 5/ColoredSheet/First Adhesive Layer 5′

[0233] An adhesive agent (Nissetsu PE-118 made by Nippon Carbide Co.,Ltd.) was coated on a silicone separator (a 50 μm thick SP-PET made byTokyo Cellophane Paper Co., Ltd.) at a dry thickness of 10 μm, and atransparent colored sheet (a 50 μm thick PET film dyed in red) waslaminated on the adhesive layer. Then, an adhesive agent (NissetsuPE-118 made by Nippon Carbide Co., Ltd.) was coated on the transparentcolored sheet at a thickness of 20 μm.

[0234] The thus obtained label for making the second multilayered volumehologram structure, from which the silicone separator was removed, waslaminated at the third adhesive layer on a substrate comprising a papersubstrate with a photograph pasted thereon, as shown in FIG. 8.

[0235] After the multilayered volume hologram structure was allowed tostand alone for 24 hours, the surface protective film 7 was strippedtherefrom.

[0236] After the release of the film 7, the surface of the hologramlayer was found to have releasing lines at intervals of 2 to 4 mm. Evenafter the surface protective film was re-laminated at the originalposition, the releasing lines were clearly visible.

[0237] Then, the third multilayered volume hologram structure of theinvention and the label for making the same is explained.

[0238] The third multilayered volume hologram structure of the inventionis explained with reference to FIG. 1 that is a front view of the firstmultilayered volume hologram structure of the invention. It is here tobe noted that FIG. 12 is a sectional view one embodiment of the thirdmultilayered volume hologram structure as taken along the A-A′ line inFIG. 1, and FIG. 13 is a sectional view illustrative of anotherembodiment of the third multilayered hologram structure.

[0239] In FIGS. 12 and 13, reference numerals 5′ and 5′ represent a heatsealing layer and an adhesive layer, respectively, and the same numeralsas in FIG. 2 indicate the same part.

[0240] As shown in FIG. 12, the third multilayered volume hologramstructure comprises a substrate 2 and a photograph of face orinformation area 4 pasted on the substrate 2 with a photographic paste3. A heat sealing layer 5′, a volume hologram layer 6, an adhesive layer5″ and a surface protective film 7 are laminated on the substrate 2 andastride the information area or photograph of face 4 in the describedorder.

[0241] The substrate 2, photographic paste 3, photograph of face orinformation area 4, volume hologram layer 6 and surface protective film7 are the same as those used with the first multilayered volume hologramstructure of the invention.

[0242] The heat sealing layer 5, for instance, may compriseethylene-vinyl acetate copolymer resin, polyamide resin, polyesterresin, polyethylene resin, ethylene-isobutyl acrylate copolymer resin,butyral resin, polyvinyl acetate and its copolymer resin, cellulosederivatives, polymethyl methacrylate resin, polyvinyl ether resin,polyurethane resin, polycarbonate resin, polypropylene resin, epoxyresin, phenol resin, thermoplastic elastomers such as SBS, SIS, SEBS andSEPS, or reaction hot-melt resins, and has preferably a thickness of 4μm to 20 μm.

[0243] The adhesive layer 5″, for instance, may again be formed ofacrylic resin, and acrylic ester resin or their copolymers as well asstyrene-butadiene copolymer, natural rubber, casein, gelatin, rosinester, terpene resin, phenolic resin, styrene resin, coumarone-indeneresin, polyvinyl ether, and silicone resin. The adhesive layer 5″ mayalso be formed of adhesives based on a-cyanoacrylate, silicone,maleimide, styrol, polyolefin, resorcinol, and polyvinyl ether. Thisadhesive layer has preferably a thickness of 4 μm to 20 μm.

[0244] What has been described in conjunction with the firstmultilayered volume hologram structure holds for the surface protectivefilm 7. As a matter of course or in view of thermal deformationtemperature, melting point, etc., however, this surface protective filmshould be stable with respect to the heat applied for heat sealing.

[0245] Upon lamination, a heating roll or the like is used to heat sealthe third multilayered volume hologram structure of the invention allover the surface thereof, but preferably only at the whole peripheralend portion thereof. The heat sealing is carried out under a temperaturecondition of 100° C. to 180° C., and preferably 120° C. to 160° C., atwhich the influence of heating on the volume hologram layer issubstantially reduced.

[0246] The adhesive force between the volume hologram and the substrateobtained by the heat sealing layer 5′ is so high that the volumehologram layer can be bonded to the substrate while it is embedded inthe heat sealing layer. If the surface protective film should beforcibly stripped from the multilayered volume hologram structure,therefore, the volume hologram layer would fracture into two portions,one opposing to the surface protective film and the other opposing tothe substrate. It is thus absolutely impossible to falsify the volumehologram layer, and the substrate such as a photograph.

[0247] Then, another embodiment of the third multilayered volumehologram structure of the invention is explained with reference to FIG.13 that is a sectional view thereof, and FIG. 14 that is a plan view ofa heat-sealed portion.

[0248] As can be seen from FIG. 13, the second embodiment of the thirdmultilayered volume hologram structure comprises a surface protectivefilm 7 and a volume hologram layer 6 having an area smaller than that ofthe surface protective film 7, so that the volume hologram layer can belaminated on substrates 2 and 4 such as a certificate while it isentirely covered by the surface protective film. As hatched in FIG. 14,only the whole peripheral end portion of the multilayered volumehologram structure including the whole peripheral portion of the volumehologram layer 5 is heat sealed.

[0249] In this multilayered structure, the adhesive force between thevolume hologram layer and the substrates obtained by the heat-sealedportion is very high, and so is the adhesive force between theheat-sealed portion and the volume hologram layer. If the surfaceprotective film should be forcibly stripped from the multilayeredstructure, therefore, the volume hologram layer would break downcertainly. Thus, if the photographic substrate should be falsified, apartial release of the volume hologram layer would be so easily detectedthat the falsification of the substrate would be absolutely impossible.

[0250] In this embodiment, it is preferable that the heat sealing layer,adhesive layer, volume hologram layer and surface protective film areall transparent.

[0251] A label for making the third multilayered volume hologramstructure of the invention is explained with reference to FIG. 15 thatis a sectional view illustrative of the layer construction thereof.

[0252] In FIG. 15, reference numerals 20 and 11 represent a label formaking the third multilayered volume hologram structure and a releasepaper, respectively, and the same numerals as in FIGS. 12 to 14 indicatelike the same parts.

[0253] A label 20 of FIG. 15 comprises a heat sealing layer 5′, a volumehologram layer 6, an adhesive layer 5″ and a surface protective film 7laminated on the release paper 11 in the described order. When the heatsealing layer 5′ is free of adhesion, the release paper 11 may bedispensed with.

[0254] For the release paper 11, use may be made of the same materialsas mentioned in conjunction with the label for making the firstmultilayered volume hologram structure of the invention. The label, fromwhich the release paper is removed, is laminated at the heat sealinglayer 51 on a substrate 2 with a photograph, etc. pasted thereon, sothat the multilayered volume hologram structure shown in FIG. 12 can befabricated.

[0255] A label 30 shown in FIG. 16 comprises an adhesive layer 5″, avolume hologram layer 6, a heat sealing layer 5′ and a surfaceprotective film 7 laminated on the release paper 11 in the describedorder. The surface protective film 7 is of such size that the hologramlayer 6 is covered thereby to the whole periphery, as shown in FIG. 13.Upon a release of the release paper 11, the label 30 is laminated at theadhesive layer 5″ on a substrate 2 with a photograph, etc. pastedthereon, and then heat sealed, so that the multilayered volume hologramstructure shown in FIG. 13 can be fabricated.

[0256] In what follows, the third multilayered volume hologram structureof the invention and the label for making the same will now be explainedwith reference to illustrative examples 6, 7 and 8.

ILLUSTRATIVE EXAMPLE 6 Preparation of Hologram-Recorded Material

[0257] A Lippmann hologram was recorded on a hologram recording mediumobtained by laminating a hologram recording material layer (a 20 μmthick Omnidex 706 made by Du Pont) and a polyvinyl chloride film on apolyethylene terephthalate film in the described order.

Preparation of Silicone Separator/Heat Sealing Layer

[0258] A heat sealing film [polyethylene film or Lix Film LIX-2 (30 μm)made by Toyobo Co., Ltd.] was laminated on a silicone separator (a 50 μmthick SP-PET made by Tokyo Cellophane Paper Co., Ltd.).

Surface Protective Film/Adhesive Layer/Silicone Separator

[0259] An adhesive agent (Nissetsu PE-118 made by Nippon Carbide Co.,Ltd.) was coated on a silicone separator (a 50 μm thick SP-PET made byTokyo Cellophane Paper Co., Ltd.) at a dry thickness of 10 μm, and anon-stretched ethylene-vinyl alcohol copolymer film (a 25 μm thick EvalEF-F made by Kuraray Co., Ltd.) was then laminated on the surface of theadhesive layer.

Preparation of Multilayered Volume Hologram Structure-Making Label

[0260] The polyvinyl chloride film was removed from thehologram-recorded material, and the aforesaid silicone separator/heatsealing layer was laminated on the hologram-recorded material to obtaina PET film/hologram layer/heat sealing layer/silicone separatormultilayered structure.

[0261] The PET film was removed from this multilayered structure whilethe silicone separator was removed from the aforesaid surface protectivelayer/adhesive layer/silicone separator structure. Then, lamination wascarried out to obtain a label for the fabrication of the multilayeredvolume hologram structure of the invention, which comprised a surfaceprotective film/adhesive layer/hologram layer/heat sealinglayer/silicone separator structure.

Preparation of Multilayered Volume Hologram Structure

[0262] Upon removal of the silicone separator, the label was laminatedat the heat sealing layer on a substrate with a photograph pastedthereon, as shown in FIG. 12.

[0263] Using a heating roll, the multilayered volume hologram structurewas heat sealed all over the surface at 150° C. for 15 seconds.

[0264] After the multilayered volume hologram structure was allowed tostand alone, the hologram layer broken down into a hologram layer piecereleased together with the surface protective film and a hologram layerpiece heat sealed onto the substrate. The photograph could not bereleased from the substrate without a breakdown of the substrate.

ILLUSTRATIVE EXAMPLE 7

[0265] The third multilayered volume hologram structure was prepared asin illustrative example 6 with the exception that the following surfaceprotective film/adhesive layer/silicone separator structure was used.

Surface Protective Film/Adhesive Layer/Silicone Separator

[0266] An adhesive agent (Nissetsu PE-118 made by Nippon Carbide Co.,Ltd.) was coated on a silicone separator (a 50 μm thick SP-PET made byTokyo Cellophane Paper Co., Ltd.) at a dry thickness of 10 μm, and atetrafluoroethylene-perfluoroalkylvinyl ether copolymer film (a 25 μmthick Toyofulone made by Toray Industries, Inc.) was then laminated onthe surface of the adhesive layer.

[0267] The obtained label for making the multilayered volume hologramstructure was used as in illustrative example 6 to prepare amultilayered volume hologram structure.

[0268] The multilayer was forcibly stripped from the multilayeredstructure as in illustrative example 6. The hologram layer broken downinto a hologram layer piece released together with the surfaceprotective film and a hologram layer piece heat sealed onto thesubstrate. The photograph could not be stripped from the substratewithout a breakdown of the substrate.

ILLUSTRATIVE EXAMPLE 8 Preparation of Hologram-Recorded Material

[0269] A Lippmann hologram was recorded on a hologram recording mediumobtained by laminating a hologram recording material layer (a 20 μmthick Omnidex 706 made by Du Pont) and a polyvinyl chloride film on apolyethylene terephthalate film in the described order.

Preparation of Silicone Separator/Adhesive Layer

[0270] An adhesive agent (Nissetsu PE-118 made by Nippon Carbide Co.,Ltd.) was coated on a silicone separator (a 50 μm thick SP-PET made byTokyo Cellophane Paper Co., Ltd.) at a dry thickness of 10 μm.

Preparation of Surface Protective Film/Heat Sealing Layer/SiliconeSeparator

[0271] A heat sealing film [a biaxially stretched polypropylene film orTrefan BOM114 made by Toray Industries, Inc.] and a non-stretchedethylene-vinyl alcohol copolymer film (a 12 μm thick Eval EF-F made byKuraray Co., Ltd.) were laminated on the silicone separator (a 50 μmthick SP-PET made by Tokyo Cellophane Paper Co., Ltd.) in the describedorder.

Preparation of Multilayered Volume Hologram Structure-Making Label

[0272] The aforesaid silicone separator/adhesive layer structure waslaminated on the aforesaid hologram-recorded material from which thepolyvinyl chloride film was removed to obtain a PET film/hologramlayer/adhesive layer/silicone separator multilayer structure.

[0273] The PET film was released from the multilayer structure while thesilicone separator was released from the surface protective film/heatsealing layer/silicone separator structure. Lamination was carried outas in FIG. 16 to obtain the multilayered volume hologramstructure-making label shown in FIG. 16 comprising a surface protectivefilm/heat sealing layer/hologram layer/adhesive layer/silicone separatorstructure.

Preparation of Multilayered Volume Hologram Structure

[0274] Upon removal of the silicone separator, the label was laminatedat the adhesive layer on a substrate with a photograph pasted thereon,as shown in FIG. 13.

[0275] After this lamination, heat sealing was carried out at 140° C.for 20 seconds, so that the volume hologram layer was covered with thesurface protective film to the whole peripheral end thereof and thesurface protective film was laminated on a substrate for a certificateor the like, whereby only the whole peripheral end of the multilayeredvolume hologram structure including the whole peripheral end of thevolume hologram layer was heat sealed.

[0276] After the multilayered volume hologram structure was allowed tostand alone, the hologram layer broken down into a hologram layer piecereleased together with the surface protective film and a hologram layerpiece remaining heat-sealed onto the substrate.

[0277] Then, the fourth multilayered volume hologram structure of theinvention and the label for making the same is explained.

[0278] One embodiment of the fourth multilayered volume hologramstructure of the invention is now -explained with reference to FIG.17(a) that is a sectional view thereof.

[0279] In FIG. 17(a), the same numerals as in FIG. 2 indicate the sameparts. Between a substrate 2 and a first adhesive layer 5′ there areinterleaved a photograph and a personal information area although notillustrated. Regions indicated at S have strong adhesive force whileregions indicated at W have weak adhesive force.

[0280] The substrate 2, a volume hologram layer 6 and a surfaceprotective film 7 are the same as those in the first multilayered volumehologram structure of the invention.

[0281] Each of the first and second adhesive layers 5′ and 5″ has anadhesive force profile in its own plane rather than is uniformly coatedthereon with only one adhesive agent. In other words, the adhesive layeris divided into regions (S) having strong adhesive force and regions (w)having weak adhesive force.

[0282] Shown in FIG. 17(b) is such an adhesive force profile. FIG. 17(a)is a view of the second adhesive layer 5″ as taken along a directionshown by A in FIG. 17(a). For instance, hatched regions S are formed ofan adhesive agent having strong adhesive force while unhatched regions Ware formed of an adhesive agent having weak adhesive force. That is, thesecond adhesive layer 5″ has a striped adhesive force profile in its ownplane. Since the adhesive agent is transparent or of the same color,however, such a striped adhesive force profile as depicted in FIG. 17(b)is invisible.

[0283] This also holds for the first adhesive layer 5′. As shown in FIG.17(a), it is preferable that regions of the layer 5′ opposing to theregions of the layer 5″ having strong adhesive force are formed of anadhesive agent having weak adhesive force while regions of the layer 5″opposing to the regions of the layer 5″ having weak adhesive force areformed of an adhesive agent having strong adhesive force.

[0284] For the adhesive agents used herein various adhesive agents areknown, for instance, elastomer adhesives such as those based on naturalrubber, reclaimed rubber, chloroprene rubber, nitrile rubber,styrene-butadiene rubber and thermoplastic elastomer; synthetic resinadhesives such as those based on epoxy resin and polyurethane; reactiontype acrylic adhesives; chemical reaction type adhesives such as thosebased on cyanoacrylate; UV curing type adhesives; EB curing typeadhesives; hot melt adhesives such as those based ethylene-vinyl acetatecopolymer resins; hot melt adhesives such as those based on polyamide,polyester, thermoplastic elastomer and reaction type hot melts; aqueousadhesives or water-soluble adhesives; emulsion adhesives; latexadhesives; and inorganic adhesives. To make a difference in the adhesiveforce of the adhesive agent, it is preferable to vary the composition,and composition ratio of the adhesive agent.

[0285] For instance, the first adhesive layer 5′ and the second adhesivelayer 5″ are each allowed to have an adhesive force profile in its ownplane by the pattern-wise coating of an acrylic adhesive agent and asilicone adhesive agent. By reducing or increasing the amount of atackifier resin known as an adhesion improver, too, it is possible toimpart an adhesive force profile to each adhesive layer.

[0286] When, for instance, the volume hologram layer 6 is forciblystripped from the multilayered volume hologram structure in a directionindicated by B in FIG. 17(a), the volume hologram layer breaks down asshown in FIG. 18, because the volume hologram layer is attracted by theadhesive layer having stronger adhesive force. Regarding FIG. 18, it isto be noted that the hatched regions (S) of the first adhesive layer 5′,and the second adhesive layer 5″ are stronger in adhesive force than theunhatched regions (W).

[0287] If the volume hologram layer 6 should be forcibly stripped fromthe multilayered volume hologram structure, the volume hologram layerwould break down or otherwise deform. Thus, even when such a defectivevolume hologram layer is copied or pasted on another substrate forfalsification, it is possible to easily tell whether it is genuine orspurious.

[0288] Thus, the ability of the fourth multilayered volume hologramstructure to prevent falsification is much higher than would beachievable so far in the art.

[0289] Another embodiment of the fourth multilayered volume hologramstructure is explained below. However, the same parts as in FIG. 17 areindicated by the reference numerals, and so are not explained.

[0290]FIG. 19 is a sectional view of the second embodiment of the fourthmultilayered volume hologram structure, which is identical with thefirst embodiment of FIG. 17(a) with the exception that a first adhesivelayer 5′ is uniformly formed by the coating of a single adhesive agent.

[0291]FIG. 20 is a sectional view of yet another embodiment of thefourth multilayered volume hologram structure, which is identical withthe first embodiment of FIG. 17(a) with the exception that a secondadhesive layer 5″ is uniformly formed by the coating of a singleadhesive agent. In these embodiments, either one of the first and secondadhesive layers may have an adhesive force profile in its own plane.Alternatively, both the first and second adhesive layers have anadhesive force profile in their own planes.

[0292] In the foregoing embodiments, the adhesive layer(s) is allowed tohave an adhesive force profile in its own plane by a striped array ofadhesive agents having strong, and weak adhesive force. Alternatively,the adhesive force profile in the plane of the adhesive layer may beobtained as shown in FIG. 21.

[0293]FIG. 21(a) is a sectional view of a further embodiment of thefourth multilayered volume hologram structure, wherein a first adhesivelayer 5′ and a second adhesive layer 5″ are each coated with a stripedarray of adhesives only at hatched regions α. FIG. 21(b) is a sectionalview of the second adhesive layer 5′ as taken along a direction shown byA in FIG. 21(a). This also holds for the first adhesive layer 5′.

[0294] Even with this arrangement, it is evident that the adhesive forceprofile can be imparted to the plane of the first adhesive layer 5′, andthe second adhesive layer 5″. If the volume hologram layer 6 should beforcibly stripped from the multilayered volume hologram structure,therefore, the volume hologram layer break down or the pattern of theadhesive layers would break down. Thus, even when such a defectivevolume hologram layer is copied or pasted on another substrate forfalsification, it is possible to easily tell whether it is genuine orspurious.

[0295] In FIG. 21, the adhesive force profile is imparted to the planesof both the adhesive layers. As a matter of course, however, it isacceptable to impart the adhesive force profile to the plane of eitherone of the adhesive layers. While the four embodiments of the fourthmultilayered volume hologram structure have been described, it is to beunderstood that the invention is not limited thereto, and so manymodifications may be made without departing from the scope of theinvention. For instance, the profile pattern of the adhesive force inthe plane of the adhesive layer is not limited to those mentioned above,and so may be determined as desired.

[0296] In these embodiments, it is preferable that the adhesive layers,volume hologram layer and surface protective film in the fourthmultilayered volume hologram structure are all transparent.

[0297] When the fourth multilayered volume hologram structure of theinvention is fabricated, a label for making the same is used.

[0298] The label for making the fourth multilayered volume hologramstructure of the invention comprises a release paper 11, and a firstadhesive layer, a volume hologram layer, a second adhesive layer and asurface protective film laminated on the release paper 11 in thedescribed order, wherein at least one of said first and second adhesivelayers is allowed to have an adhesive force profile in its own plane.

[0299] The release paper 11 used herein may be the same as that for thefirst multilayered volume hologram structure of the invention. Uponremoval of this release paper, the label is laminated at the firstadhesive layer 5′ on a substrate 2 with a photograph, etc. pastedthereon, so that the fourth multilayered volume hologram structure canbe fabricated.

[0300] Next, the fifth multilayered volume hologram structure of theinvention and the label for making the same are explained.

[0301] The fifth multilayered volume hologram structure of the inventionis explained with reference to FIG. 1 that is a front view of the firstmultilayered volume hologram structure of the invention as well as FIG.22 that is a sectional view of the fifth multilayered volume hologramstructure as taken along the A-A line in FIG. 1 and FIG. 23 that is asectional view of another embodiment of the fifth multilayered volumehologram structure.

[0302] In FIGS. 22 and 23, a third adhesive layer, a first adhesivelayer, a second adhesive layer, a colored sheet, and a microcapsule areindicated at 5, 5′, 5″, 9, and 10 respectively, and the same numerals asin FIG. 2 indicate the same parts.

[0303] As can be seen from FIG. 22, the fifth multilayered volumehologram structure comprises a personal information area and photographof face 4 pasted on a substrate 2 with a photographic paste 3. The firstadhesive layer 5′ containing microcapsules 10, volume hologram layer 6,adhesive layer 5″ containing microcapsules 10 and surface protectivelayer 7 are laminated on the substrate 2 and astride photograph 4 in thedescribed order.

[0304] The substrate 2, photographic paste 3, photograph of face andpersonal information area 4, volume hologram layer 6 and surfaceprotective film 7 are the same as those in the first multilayered volumehologram structure of the invention.

[0305] In the fifth multilayered volume hologram structure of theinvention, the first and second adhesive layers 5′ and 5″ are eachcomprised of an adhesive agent and a micro-capsule in which a volumehologram layer-breaking material is encapsulated in a skin materialselected from various polymer materials.

[0306] The adhesive layer used herein is formed of acrylic resin,acrylic ester resin, and vinyl acetate resin or their copolymers as wellas styrene-butadiene copolymer, natural rubber, casein, gelatin, rosinester, terpene resin, phenolic resin, styrene resin, coumarone-indeneresin, polyvinyl ether, and silicone resin. The adhesive layer 5 mayalso be formed of adhesives based on α-cyanoacrylate, silicone,maleimide, styrol, polyolefin, resorcinol, and polyvinyl ether.

[0307] Each or the microcapsule has a capsule structure in which thevolume hologram layer-breaking material is encapsulated in the skinmaterial selected from various polymer materials. The microcapsulebreaks down simultaneously with a release of the volume hologram layer,and the volume hologram layer-breaking material therein is released inthe adhesive layer to solubilize or swell the volume hologram layer, sothat the hologram recorded in the volume hologram layer can break down.

[0308] When the volume hologram layer-forming material is composed ofthe matrix polymer, photopolymerizable compound, photopolymerizationinitiator and sensitizing dye, all already explained in detail, it ispreferable to use as the volume hologram layer-breaking material anorganic solvent in which the volume hologram layer-forming material issoluble and/or a plasticizer that has a swelling action on the volumehologram layer.

[0309] Exemplary such organic solvents are acetone, methyl ethyl ketone,methyl isobutyl ketone, cyclohexanone, benzene, toluene, xylene,chlorobenzene, tetrahydrofuran, methyl cellosolve, ethyl cellosolve,methyl cellosolve acetate, ethyl cellosolve acetate, ethyl acetate,1,4-dioxane, 1,2-dichloroethane, dichloromethane, chloroform, methanol,ethanol, and isopropanol, or mixtures thereof.

[0310] The plasticizers having a swelling action on the volume hologramlayer, for instance, include polyhydric alcohols such as ethyleneglycol, diethylene glycol, triethylene glycol, glycerin, andtrimethylolpropane; and phthalic ester plasticizers such as dimethylphthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP),heptylnonyl phthalate (HNP), di(2-ethylhexyl) phthalate (DOP),di(n-octyl) phthalate (DNOP), di(i-octyl) phthalate (DCapP), (79 alkyl)phthalate (D79P), di(i-decyl) phthalate (DIDP), di-tridecyl phthalate(DTDP), dicyclohexyl phthalate (DCHP), butylbenzyl phthalate (BDP),ethyl phthalyl ethyl glycolate (DPEG), and butyl phthalyl butylglycolate (BPBG); aliphatic dibasic acid ester plasticizers such asdi(2-ethylhexyl) adipate (DOA), di(methylcyclohexyl) adipate,di-isodecyl adipate (DIDA), di(n-hexyl) azelate (DNHZ), di-2-ethylhexylazelate (DOZ), dibutyl sebacate (DBS) and di(2-ethylhexyl) sebacate(DOS); citric ester plasticizers such as triethyl citrate (TEC),tributyl citrate (TBC), acetyl triethyl citrate (ATEC) and acetyltributyl citrate (ATBC); epoxy plasticizers such as epoxidized soy beanoil; and phosphoric ester plasticizers such as tributyl phosphate (TBP),triphenyl phosphate (TPP), tricresyl phosphate (YCP) and tripropyleneglycol phosphate. Mixtures of the plasticizers mixed with or dissolvedin the organic solvents may also be used.

[0311] The skin materials used herein for microcapsule formation, forinstance, include gum arabic; acrylic high-molecular compounds such aspolyacrylamide, polyacryldextrin, poly(alkylcyano) acrylate andpolymethyl methacrylate; agar and agarose; albumin; alginates such ascalcium alginate and sodium alginate; aluminum monostearate; carboxymonostearate; carboxyvinyl high-molecular compounds; epoxy resin;cellulose derivatives such as cellulose acetate, cellulose acetatebutyrate, cellulose acetate phthalate, cellulose nitrate, ethylcellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose,hydroxypropylmethyl cellulose phthalate, methyl cellulose, sodiumcarboxymethyl cellulose and nitrocellulose; cetyl alcohol; dextrin;gelatin; hydrogenated tallow; hydrogenated castor oil; 12-hydroxystearylalcohol; gluten; glycerin monopalmitate and glycerin dipalmitate;glycerin monostearate, glycerin distearate and glycerin tristearate;myristyl alcohol; nylon 6, nylon 7, nylon 8, nylon 9 and nylon 10;poly(adipyl L-lysine); polyterephtalamide; poly(terephthaloyl L-lysine);polyurea; polyurethane; polyisoprene; polyether; polyethylene;polypropylene; poly(ε-caprolactone); polydimethylsiloxane; polyester;polyethylene glycol; poly(ethylene-vinyl acetate); polyglycolic acid;polylactic acid; polyglutamic acid; polysiloxane; polybutadiene;polylysine; poly(methyl vinyl ether-maleic anhydride); polystyrene;polyvinyl acetate phthalate; polyvinyl alcohol; polyvinyl pyrrolidone;shellac; starch and its derivatives; stearic acid; stearyl alcohol;waxes such as beewax, carnauba wax, Japan wax, paraffin wax andspermaceti; and inorganic silicates.

[0312] As a matter of course, these materials to form the skin materialof the microcapsule should not be dissolved in the volume hologramlayer-breaking material or the adhesive layer component. Anotherrequirement for the materials is to have such a strength that they breakdown upon a release of the adhesive layer.

[0313] The microcapsule may be prepared by known polymerizationprocesses such as interface polymerization, in situ polymerization, andcoacervation, and have a diameter of 0.001 μm to 20 μm, and preferably0.01 μm to 1 μm. A microcapsule having too small a diameter is notpreferable because it fails to break down effectively. A microcapsulehaving too large a diameter is again not preferred because it rendersthe formation of the adhesive layer by coating difficult, or it mayoften break down.

[0314] The microcapsules are used in an amount of 1 part by weight to100 parts by weight, and preferably 10 parts by weight to 50 parts byweight per 100 parts by weight of the adhesive agent. The adhesive layermay be formed by the mixing and dispersion of the microcapsules with andin the adhesive layer-forming material. For coating, use may be made ofsuitable coating processes such as dip coating, die coating, spraycoating, roll coating, and gravure coating.

[0315] Each adhesive layer has preferably a thickness of 4 μm to 20 μmas measured upon coating.

[0316] Next, another embodiment of the fifth multilayered volumehologram structure according to the invention is explained withreference to FIG. 23. In FIG. 23, reference numerals 9 and 5 represent acolored sheet and a third adhesive layer, respectively, and the samereference numerals as in FIG. 22 indicate the same parts or elements.

[0317] As can be seen from FIG. 23, the second embodiment of the fifthmultilayered volume hologram structure according to the inventioncomprises a substrate and a colored sheet 9 with the third adhesivelayer 5 interleaved therebetween. A first adhesive layer 5′ containingmicrocapsules, a volume hologram layer 6, a second adhesive layer 5″containing microcapsules and a surface protective film 7 are laminatedon the colored sheet 9 in the described order.

[0318] For the colored sheet 9 use may be made of a polyester, triacetylcellulose, polypropylene or acrylic film dyed with a dye or pigment thathas no adverse influence on the volume hologram recorded layer. When itis required to see something through the colored sheet as in the casewhere it is laminated on the photograph as shown in FIG. 3, the coloredsheet must be transparent although depending on the type of thesubstrate on which the colored sheet is to be laminated. When this isnot required, an opaque colored sheet may be used. The colored sheet haspreferably a thickness of 10 μm to 100 μm.

[0319] When a black colored sheet having a color different from or incomplementary relation to the color of the hologram is used as thecolored sheet 9, it is possible to enhance the contrast of the hologramimage.

[0320] It is not always required to incorporate microcapsules in thethird adhesive layer 5 between the colored sheet 9 and the substrate 2;the third adhesive layer 5 may be formed of the aforesaid adhesivelayer-forming material as is the case with the first adhesive layer 5′,and the second adhesive layer 5″.

[0321] In this embodiment of the fifth multilayered volume hologramstructure, it is preferred that the first and second adhesive layers,each containing microcapsules, volume hologram layer and surfaceprotective film are all transparent.

[0322] Next, a label for making the fifth multilayered volume hologramstructure according to the invention is explained with reference toFIGS. 24(a) and 24(b) that are sectional views of the multilayeredconstruction thereof. In FIGS. 24(a) and 24(b), reference numerals 20and 11 represent a label for making the multilayered volume hologramstructure and a release paper, respectively, and the same referencenumerals as in FIGS. 22 and 23 indicate the same parts.

[0323] A label 20 of FIG. 24(a) comprises a first adhesive layer 5′containing microcapsules, a volume hologram layer 6, a second adhesivelayer 5″ containing microcapsules and a surface protective film 7laminated on the release paper 11 in the described order.

[0324] The release paper 11 may be the same as mentioned in conjunctionwith the label for making the first multilayered volume hologramstructure of the invention. Upon removal of the release paper, the labelis laminated at the first adhesive layer 5′ on a substrate 2 with aphotograph, etc. pasted thereon, so that the fifth multilayered volumehologram structure can be prepared.

[0325] A label 20 of FIG. 24(b) comprises a third adhesive layer 5, acolored sheet 9, a first adhesive layer 5′ containing microcapsules, avolume hologram layer 6, a second adhesive layer 5″ and a surfaceprotective film 7 laminated on the release paper 11 in the describedorder.

[0326] The release paper 11 may be the same as mentioned in conjunctionwith the label for making the first multilayered volume hologramstructure of the invention. Upon removal of the release paper, the labelis laminated at the third adhesive layer 5 on a substrate 2 with aphotograph, etc. pasted thereon, so that another embodiment of the fifthmultilayered volume hologram structure can be prepared.

[0327] In what follows, the fifth multilayered volume hologram structureof the invention and the label for making the same will be explainedwith reference to illustrative examples 9 and 10.

ILLUSTRATIVE EXAMPLE 9 Preparation of Hologram-Recorded Layer

[0328] A Lippmann hologram was recorded on a hologram recording mediumobtained by laminating a hologram recording material layer (a 20 μmthick Omnidex 706 made by Du Pont) and a polyvinyl chloride film on apolyethylene terephthalate film in the described order.

Preparation of Silicone Separator/First Adhesive Layer 5′

[0329] Fifteen (15) wt. % of microcapsules prepared by an interfacepolymerization process and having a diameter of 0.5 μm, whereinchloroform was encapsulated in a polyurethane skin material, wasdispersed in an adhesive agent (Nissetsu PE-118 made by Nippon CarbideCo., Ltd.), and the thus obtained adhesive layer was then coated by adie coating process on a silicone separator (a 50 μm thick SP-PET madeby Tokyo Cellophane Paper Co., Ltd.) at a dry film thickness of 20 μm.

Surface Protective Film/Second Adhesive Layer 5″/Silicone Separator

[0330] Fifteen (15) wt. % of microcapsules prepared by an interfacepolymerization process and having a diameter of 0.5 μm, whereinchloroform was encapsulated in a polyurethane skin material, wasdispersed in an adhesive agent (Nissetsu PE-118 made by Nippon CarbideCo., Ltd.), and the thus obtained adhesive layer was then coated by adie coating process on a silicone separator (a 50 μm thick SP-PET madeby Tokyo Cellophane Paper Co., Ltd.) at a dry film thickness of 20 μm.Then, a non-stretched ethylene-vinyl alcohol copolymer film (a 25 μmthick Eval EF-F made by Kuraray Co., Ltd.) were laminated on the surfaceof the adhesive layer.

Preparation of Multilayered Volume Hologram Structure-Making Label

[0331] The silicone separator/first adhesive layer 5′ structure waslaminated on the hologram-recorded material from which the polyvinylchloride film was removed to obtain a PET film/hologram layer/firstadhesive layer 5′/silicone separator multilayered structure.

[0332] The PET film was released from the multilayered structure whilethe silicone separator was released from the surface protectivefilm/second adhesive layer 5″/silicone separator structure. Laminationwas carried out to obtain the multilayered volume hologramstructure-making label shown in FIG. 24(a) comprising a surfaceprotective film/second adhesive layer 5″/hologram layer 6/first adhesivelayer 5″/silicone separator structure.

Preparation of Multilayered Volume Hologram Structure

[0333] Upon removal of the silicone separator from the label, the labelwas laminated at the first adhesive layer 5′ on a paper substrate with aphotograph pasted thereon, as shown in FIG. 22.

[0334] After the multilayered structure was allowed to stand alone for24 hours, the volume hologram layer 6 was released from the firstadhesive layer 5′.

[0335] The volume hologram layer was again laminated at the originalposition and allowed to stand alone for a further 24 hours to observethe recorded hologram. Consequently, it was clearly found that theoriginal hologram image was partly disturbed and broken by the solventflowing out of the broken microcapsules.

ILLUSTRATIVE EXAMPLE 10

[0336] A multilayered volume hologram structure as shown in FIG. 23 anda multilayered volume hologram structure-making label as shown in FIG.24(b) were prepared as in illustrative example 9 with the exception thatthe following silicone separator/third adhesive layer 5/coloredsheet/first adhesive layer 5′ structure was used instead of the siliconeseparator/first adhesive layer 5′ structure.

Preparation of Silicone Separator/Third Adhesive Layer 5/ColoredSheet/First Adhesive Layer 5′

[0337] An adhesive agent (Nissetsu PE-118 made by Nippon Carbide Co.,Ltd.) was coated on a silicone separator (a 50 μm thick SP-PET made byTokyo Cellophane Paper Co., Ltd.) at a dry film thickness of 10 μm, anda transparent colored sheet (a 50 μm thick PET film dyed in red) wasthen laminated on the thus obtained adhesive layer. Fifteen (15) wt. %of microcapsules prepared by an interface polymerization process andhaving a diameter of 0.5 μm, wherein chloroform was encapsulated in apolyurethane skin material, was dispersed in an adhesive agent (NissetsuPE-118 made by Nippon Carbide Co., Ltd.), and the thus obtained adhesivelayer was then coated by a die coating process on the transparentcolored sheet at a dry film thickness of 20 μm.

[0338] After the multilayered structure of FIG. 23 was allowed to standalone for 24 hours, the volume hologram layer 6 was released from thesecond adhesive layer 5″.

[0339] The volume hologram layer was again laminated at the originalposition and allowed to stand alone for a further 24 hours to observethe recorded hologram. Consequently, it was clearly found that theoriginal hologram image was partly disturbed and broken by the solventflowing out of the broken microcapsules.

[0340] Next, the sixth multilayered volume hologram structure of theinvention and the label for making the same are explained.

[0341] The sixth multilayered volume hologram structure of the inventionis explained with reference to FIG. 1 that is a front view of the firstmultilayered volume hologram structure as well as FIG. 25 that is asectional view of the sixth multilayered volume hologram structure astaken along the A-A line in FIG. 1 and FIG. 26 that is a sectional viewof another embodiment of the sixth multilayered volume hologramstructure. In FIGS. 25 and 26, the same reference numerals as in FIG. 2indicate the same parts.

[0342] As shown in FIG. 25, one embodiment of the sixth multilayeredvolume hologram structure comprises a substrate 2 and a personalinformation area or photograph of face 4 pasted on the substrate with aphotographic paste 3. A first adhesive layer 5′, a volume hologram layer6 containing fine particles and a surface protective film 7 arelaminated on and astride the substrate 2 and personal information areaor photograph of face 4 in the described order.

[0343] The substrate 2, photographic paste 3, photograph of face orpersonal information area 4 and surface protective film 7 may be thesame as mentioned in conjunction with the first multilayered volumehologram structure.

[0344] For instance, the adhesive agents used herein are acrylic resin,acrylic ester resin, and vinyl acetate resin or their copolymers as wellas styrene-butadiene copolymer, natural rubber, casein, gelatin, rosinester, terpene resin, phenolic resin, styrene resin, coumarone-indeneresin, polyvinyl ether, and silicone resin. The adhesive agent may alsobe adhesives based on a-cyanoacrylate, silicone, maleimide, styrol,polyolefin, resorcinol, and polyvinyl ether as well as heat-sealingadhesives such as ethylene-vinyl acetate copolymer resin, polyamideresin, polyester resin, polyethylene resin, ethylene-isobutyl acrylatecopolymer resin, butyral resin, polyvinyl acetate and its copolymerresin, cellulose derivatives, polymethyl methacrylate resin, polyvinylether resin, polyurethane resin, polycarbonate resin, polypropyleneresin, epoxy resin, phenol resin, thermoplastic elastomers such as SBS,SIS, SEBS and SEPS, or reaction hot-melt resins. The adhesive layer haspreferably a thickness of 4 μm to 20 μm.

[0345] The recording material for the volume hologram layer 6 may be thesame as explained in conjunction with the first multilayered volumehologram structure. For the purpose of making the volume hologram layerbrittle or fragile, however, fine particles having an average primaryparticle diameter of 1 nm to 100 nm are used in an amount of 10 parts byweight to 100 parts by weight, and preferably 30 parts by weight to 60parts by weight per 100 parts by weight of photosensitive material.

[0346] For the fine particles, for instance, use may be made ofinorganic fine particles such as calcium carbonate, talc, china clay,kaolin, microsilica, titanium dioxide, glass flakes, asbestos,agalmatolite powders, silica powders, barium sulfate, and chamotte, andfor a fluorescent material emitting fluorescence upon irradiation withultraviolet radiation, use may be made of a so-called synthetic resinsolid solution type of daylight fluorescent pigment. Such a daylightfluorescent pigment may be obtained by dissolving a fluorescent dye,e.g., Brilliant sulfoflavine FF (C.I. 56205), Basic yellow (C.I. 46060),Eosine (C.I. 45380), Rhodamine 6G (C.I. 45160), and Rhodamine B (C.I.45170) in a carrier resin, e.g., methacrylic ester, polyvinyl chloride,vinyl chloride-vinyl acetate copolymer, polyamide resin, alkyd resin,aromatic sulfonamide, urea resin, melamine resin, benzoguanamine resin,and a resin obtained by the cocondensation and copolymerization of theseresins, and granulating the resulting solution to the aforesaid particlediameter. As the carrier resin used with the fluorescent dye in thiscase, however, it is necessary to employ a resin incompatible with thehologram-recorded material or the solvent used for the formation of sucha hologram layer as will be described later.

[0347] Fine particles having an average primary particle diameter ofsmall than 1 nm are insufficient for a brittle breakdown of thehologram-recorded layer, and so are not preferable. Fine particleshaving an average primary particle size exceeding 100 nm are again notpreferable because they act as a sort of noise with respect to therecorded hologram. When the amount of the fine particles is smaller than10 parts by weight per 100 parts by weight of photosensitive material,the objects of the invention are unachievable. On the other hand, thefine particles used in an amount exceeding 100 parts by weight act as asort of noise with respect to the recorded hologram, and so are notpreferable.

[0348] By the incorporation of fluorescent fine particles in the volumehologram layer, it is possible not only to embrittle the volume hologramlayer but also to make use of fluorescent emission upon irradiation withultraviolet radiation, thereby increasing the security of themutlilayered volume hologram structure of the invention.

[0349] The hologram recording material may be formed by dispersing theaforesaid fine particles in the coating solution referred to inconjunction with the first multilayered volume hologram structure of theinvention, and applying the coating solution onto a substrate at apost-drying thickness of 1 μm to 100 μm, and preferably 4 μm to 20 μm.

[0350] In the second embodiment of the sixth multilayered volumehologram structure, plastic particles or glass beads having a refractiveindex almost equal to that of the photosensitive material in thehologram recording layer are used in an amount of 10 parts by weight to100 parts by weight per 100 parts by weight per the photosensitivematerial instead of the aforesaid fine particles. The plastic particlesor glass beads in an amount exceeding 100 parts by weight act as a sortof noise with respect to the recorded hologram, and so are notpreferable.

[0351] The photosensitive material forming part of the volume hologramlayer has usually a refractive index of 1.4 to 1.7. For instance,divinylbenzene type plastic particles, benzoguanamine type plasticparticles, polystyrene particles, silica particles, and glass beads, allhaving a refractive index of 1.5, are exemplified as the plasticparticles, and glass beads having a corresponding refractive index. Itis thus preferable to make a sensible selection from materials having arefractive index substantially equal to that of the photosensitivematerial. Preferable particle diameters of the plastic particles orglass beads range from 1 μm to 20 μm. Diameters exceeding 20 μm makenoises with respect to the recorded hologram, and so are not preferable.A brittle breakdown of the sixth multilayered volume hologram structuremay be caused by decreasing the film strength of the volume hologramlayer as is the case with the first multilayered volume hologramstructure of the invention.

[0352] The hologram may be recorded in the same manner as explained inconjunction with the first multilayered volume hologram structure of theinvention.

[0353] Yet another embodiment of the sixth multilayered volume hologramstructure is shown in FIG. 26 wherein reference numerals 5′ and 5″represent a first adhesive layer and a second adhesive layer,respectively, and the same numerals as in FIG. 25 indicate the sameparts.

[0354] As can be seen from FIG. 26, the third embodiment of thismultilayered structure comprises a volume hologram layer 6 and a surfaceprotective film 7 laminated on the volume hologram layer with the secondadhesive layer 5″ interleaved therebetween. It is here to be noted thatthe first and second adhesive layers 5′ and 5″ may be formed either ofthe same adhesive agent or of different adhesive agents. When the heatsealing agent is used as the adhesive agent, a heating roll or the likemay be used to heat seal the whole surface of the multilayeredstructure, but preferably only the whole peripheral end portion thereof.The heat sealing is carried out at a temperature of 100° C. to 180° C.,and preferably 120° C. to 160° C. at which the influence of heating onthe volume hologram layer can be reduced.

[0355] For the sixth multilayered volume hologram structure of theinvention, it is preferable that the adhesive layers, volume hologramlayer and surface protective film are all transparent.

[0356] A label for making the sixth multilayered volume hologramstructure of the invention is explained with reference to FIGS. 27(a)and 27(b) that are sectional views thereof.

[0357] In FIGS. 27(a) and 27(b), reference numerals 10 and 11 representa multilayered volume hologram structure-making label and a releasepaper, respectively, and the same numerals as in FIGS. 25 and 26indicate the same parts.

[0358] A label 10 of FIG. 27(a) comprises an adhesive layer 5, a volumehologram layer 6 and a surface protective film 7 laminated on therelease paper 11 in the described order. When the first adhesive layer 5is a heat sealing layer, the release paper 11 may be dispensed with.

[0359] The release paper 11 may be the same as explained in conjunctionwith the label for making the first multilayered volume hologramstructure of the invention. Upon removal of the release paper, the labelis laminated at the first adhesive layer 5′ on a substrate 2 with aphotograph, etc. pasted thereon, so that a multilayered volume hologramstructure can be obtained.

[0360] A label of FIG. 27(b) comprises a first adhesive layer 5′, avolume hologram layer 6, a second adhesive layer 5″ and a surfaceprotective film 7 laminated on the release paper 11 in the describedorder. Upon removal of the release paper 11, the label is laminated atthe first adhesive layer 5′ on a-substrate 2 with a photograph, etc.pasted thereon, so that a multilayered volume hologram structure can beobtained.

[0361] In what follows, the sixth multilayered volume hologram structureof the invention and the label for making the same will be explainedwith reference to illustrative examples 11 and 12.

ILLUSTRATIVE EXAMPLE 11 Preparation of Hologram-Recorded Material

[0362] A coating solution consisting of 100 parts of Omnidex 352 made byDu Pont (composed of 25 parts of photosensitive material, 55 parts ofmethyl ethyl ketone and 20 parts of toluene) and 20 parts of fineparticles [reactive microgel (an acrylic type high-molecular colloidhaving an average primary particle diameter of 50 nm)] was coated on a50 μm thick PET film (Lumirror T-60 made by Toray Industries, Inc.) at apost-drying thickness of 25 μm. Then, a 50 μm thick ethylene-vinylalcohol copolymer film (Eval EF-E made by Kuraray Co., Ltd.) waslaminated on the surface of the obtained recording layer to form ahologram recording medium.

[0363] Using a Lippmann hologram making machine (Omnidex Copiermanufactured by Du Pont) together with 514 nm Ar laser, a reflectiontype hologram diffraction grating was fabricated.

[0364] Then, the hologram diffraction grating was irradiated with 1mW/cm² ultraviolet radiation generated from a high pressuremercury-vapor lamp for 100 seconds, and heat treated at 120° C. for 120minutes.

Preparation of Silicone Separator/Adhesive Layer

[0365] An adhesive agent (Nissetsu PE-118 made by Nippon Carbide Co.,Ltd.) was coated on a silicone separator (a 50 μm thick SP-PET made byTokyo Cellophane Paper Co., Ltd.) at a dry thickness of 10 μm.

Preparation of Surface Protective Film/Adhesive Layer/Silicone Separator

[0366] An adhesive agent (Nissetsu PE-118 made by Nippon Carbide Co.,Ltd.) was coated on a silicone separator (a 50 μm thick SP-PET made byTokyo Cellophane Paper Co., Ltd.) at a dry thickness of 10 μm, and apolyethylene terephthalate film (a 50 μm thick HP-7 made by TeijinLimited.) was then laminated on the surface of the adhesive layer.

Preparation of Multilayered volume Hologram Structure-Making Label

[0367] The ethylene-vinyl alcohol copolymer film (Eval EF-E made byKuraray Co., Ltd.) was removed from the hologram-recorded material, andthe aforesaid silicone separator/adhesive layer was laminated on thehologram recorded material to obtain a PET film/hologram layer/adhesivelayer/silicone separator multilayer structure.

[0368] The PET film was removed from this multilayer structure while thesilicone separator was removed from the aforesaid surface protectivelayer/adhesive layer/silicone separator structure. Then, lamination wascarried out to obtain a multilayered volume hologram structure-makinglabel of FIG. 27(b), which comprised a surface protective film/adhesivelayer/hologram layer/adhesive layer/silicone separator structure.

Preparation of Multilayered Volume Hologram Structure

[0369] Upon a release of the silicone separator, the label was laminatedat the adhesive layer on a paper substrate with a photograph pastedthereon, as shown in FIG. 26.

[0370] After the multilayered volume hologram structure was allowed tostand alone for 24 hours, the multilayer structure was forcibly releasedtherefrom. Consequently, the volume hologram layer fractured into piecesor broke down in the multilayered structure.

ILLUSTRATIVE EXAMPLE 12

[0371] Another sixth multilayered volume hologram structure and a labelfor making the same were prepared as in illustrative example 11 with theexception that the fine particles in the hologram recording materialwere changed to glass beads (having a refractive index of 1.5 and aparticle diameter of 4.0 μm).

[0372] It is here to be noted that when the hologram recording materialof illustrative example 11 was formed of the photosensitive materialalone, i.e., with no addition of fine particles, the photosensitivematerial layer was found to have a refractive index of 1.51.

[0373] Upon a release of the silicone separator, the label was laminatedat the adhesive layer on a paper substrate with a photograph pastedthereon, as shown in FIG. 26.

[0374] After the multilayered volume hologram structure was permitted tostand alone for 24 hours, the multilayer structure was forcibly releasedtherefrom. Consequently, the volume hologram layer fractured into piecesor broke down in the multilayered structure.

[0375] Next, the seventh multilayered volume hologram structure of theinvention and the label for making the same are explained.

[0376] The seventh multilayered volume hologram structure of theinvention is explained with reference to FIG. 1 that is a front view ofthe first multilayered volume hologram structure of the invention aswell as FIG. 28 that is a sectional view of the seventh multilayeredvolume hologram structure as taken along the A-A line in FIG. 1 and FIG.29 that is a sectional view of another embodiment of the seventhmultilayered volume hologram structure. In FIGS. 28 and 29, referencenumeral 9 stands for a monomer or plasticizer-containing resin orbrittle layer. The same numerals as in FIG. 2 indicate the same parts.

[0377] One embodiment of the seventh multilayered volume hologramstructure comprises a substrate 2 and a personal information area orphotograph of face 4 pasted on the substrate 2 with a photographic paste3, as can be seen from FIG. 28. An adhesive layer 5, a volume hologramlayer 6, a monomer or plasticizer-containing resin or brittle layer 9and a surface protective film 7 are laminated on the substrate 2 andastride the photograph of face 4.

[0378] The substrate 2, photographic paste 3, photograph of face orpersonal information area 4, volume hologram layer 6 and surfaceprotective film 7 may be the same as explained in conjunction with thefirst multilayered volume hologram structure of the invention, and theadhesive layer may be the same as explained in conjunction with thesixth multilayered volume hologram structure of the invention.

[0379] For the resin in the monomer or plasticizer-containing resinlayer 9, for instance, use may be made of polyethylene terephthalate,cellulose acetate, polyvinyl chloride, polyethylene, polymethylmethacrylate, and polyvinyl acetate.

[0380] For the monomer contained in the resin layer, use may be made ofphotopolymerizable and photo-crosslinkable monomers, oligomers, andprepolymers having at least one ethylenically unsaturated bond permolecule as already mentioned in conjunction with the hologram-formingmaterial in the first multilayered volume hologram structure of theinvention, and their mixtures. For instance, unsaturated carboxylicacids and their salts, esters of unsaturated carboxylic acids andaliphatic polyhydric alcohol compounds, and amide combinations ofunsaturated carboxylic acids and aliphatic polyhydric amine compoundsmay be exemplified. Exemplary monomers for the unsaturated carboxylicacids are acrylic acid, methacrylic acid, itaconic acid, crotonic acid,isocrotonic acid, and maleic acid, which may have halogen substituentsas in the case of chlorinated unsaturated carboxylic acids, brominatedunsaturated carboxylic acids, and fluorinated unsaturated carboxylicacids. Exemplary salts of the unsaturated carboxylic acids are sodium,and potassium salts of the aforesaid acids. For specific examples, seethose mentioned in conjunction with the first multilayered volumehologram structure of the invention.

[0381] The monomers may be incorporated in the resin layer in an amountof 1% by weight to 90% by weight, and preferably 5% by weight to 50% byweight, thereby forming a coating solution. For instance, a solution ofthe resin and monomer dissolved in a mixed solvent (methyl ethylketone:toluene=1:1) may be coated on the volume hologram layer at apost-drying thickness of 1 μm to 100 μm, and preferably 3 μm to 30 μm bymeans of gravure coating, roll coating, blade coating, die coating orthe like. Alternatively, the coating solution may be formed into film,which is in turn laminated on the volume hologram layer.

[0382] The plasticizer-containing resin layer may be used in place ofthe monomer-containing resin layer 9. For the resin in theplasticizer-containing resin layer, for instance, use may be made ofpolyethylene terephthalate, cellulose acetate, polyvinyl chloride,polyethylene, polymethyl methacrylate, and polyvinyl acetate.

[0383] For the plasticizer, use may be made of those mentioned inconjunction with the fifth multilayered volume hologram structure of theinvention.

[0384] The amount of the plasticizer contained in the resin layer is inthe range of 0.1% by weight to 50% by weight, and preferably 5% byweight to 30% by weight.

[0385] The plasticizer-containing resin layer 9 may be provided bycoating a solution of the resin and plasticizer dissolved in a mixedsolvent (methyl ethyl ketone:toluene=1:1) on the volume hologram layerat a post-drying thickness of 1 μm to 100 μm, and preferably 3 μm to 30μm by gravure coating, roll coating, blade coating, die coating or thelike. Alternatively, the coating solution may be formed into film, whichis in turn laminated on the volume hologram layer.

[0386] Another embodiment of the seventh multilayered volume hologramstructure of the invention is shown in FIG. 29 wherein 5′ and 5″indicate adhesive layers, and the same numerals as in FIG. 28 indicatethe same parts.

[0387] In the second embodiment of the seventh multilayered volumehologram structure of the invention, a surface protective film 8 islaminated on a monomer or plasticizer-containing resin layer 9 with theadhesive layer 5″ interleaved between them, as shown in FIG. 29. Theadhesive layers may be the same as explained in conjunction with thesixth multilayered volume hologram structure of the invention, and theadhesive layers 5′ and 5″ may be formed of the same adhesive agent ordifferent adhesive agents.

[0388] After constructed as mentioned above, the seventh multi-layeredvolume hologram structure of the invention is preferably heat treated at80° C. to 160° C. for 1 minute to 300 minutes. This allows the monomeror plasticizer to come out of the resin layer 9, so that the volumehologram layer 6 adjacent to the resin layer 9 can be easily releasedtherefrom, thereby ensuring prevention of falsification. Since themonomer or plasticizer passes into the volume hologram layer, it ispossible to alter the peak wavelength of the volume hologram or widenthe diffraction wavelength range of the volume hologram.

[0389] Next, yet another embodiment of the seventh multilayered volumehologram structure is similar to the first embodiment thereof shown inFIG. 28 with the exception that the monomer or plasticizer-containingresin layer 9 is changed to a brittle layer 9. This embodiment, too, hasthe ability to prevent falsification.

[0390] The brittle layer 9 comprises a resin and fine particlescontained therein. For the resin, use may be made of a homopolymer orcopolymer resin of styrene resin such as poly-α-methylstyrene; ahomopolymer or copolymer resin of acrylic or methacrylic resin such aspolymethyl methacrylate, polyethyl methacrylate, polymethyl acrylate,polyethyl acrylate, and polybutyl acrylate; a cellulose derivative suchas ethyl cellulose, nitrocellulose, hydroxyethyl cellulose, celluloseacetate propionate, cellulose acetate butyrate, and cellulose acetate;one of polyvinyl alcohol, polyvinyl acetate, polyvinyl chloride,polypropylene, polyethylene and polyether resins or mixtures orcopolymers of two or more thereof; and a heat-curing resin such asphenolic resin, urea resin, and melamine resin.

[0391] For the fine particles contained in the resin, for instance, usemay be made of inorganic fine particles such as calcium carbonate, talc,china clay, kaolin, microsilica, titanium dioxide, glass flakes,asbestos, agalmatolite powders, silica powders, barium sulfate, andchamotte.

[0392] Preferably, the amount of the fine particles to be contained inthe resin is in the range of 80 parts by weight to 200 parts by weightper 100 parts by weight of resin. The brittle layer has preferably athickness of 4 μm to 40 μm.

[0393] If the seventh multilayered volume hologram structure should bedelaminated for the purpose of falsification, the protective film wouldbe easily released from the volume hologram layer with or without theresin layer 9, while the volume hologram layer would remain fixed to thesubstrate 2 or the photograph 4. If, in this case, the remaininghologram layer 6 should be forcibly stripped from the photograph, thehologram layer would break down certainly because of its softness andbrittleness.

[0394] In the seventh multilayered volume hologram structure, it ispreferable that the adhesive layer, volume hologram layer, resin layerand surface protective film are all transparent.

[0395] A label for making the seventh multilayered volume hologramstructure is explained with reference to FIGS. 30(a) and 30(b) that aresectional views of the multilayered construction thereof.

[0396] In FIGS. 30(a) and 30(b), reference numerals 10 and 11 representa multilayered volume hologram structure-making label and a releasepaper, respectively, and the same numerals as in FIG. 29 indicate thesame parts.

[0397] A label 10 of FIG. 30(a) comprises an adhesive layer 5, a volumehologram layer 6, a monomer or plasticizer-containing resin layer 9 anda surface protective film 7 laminated on the release paper 11 in thedescribed order.

[0398] The release paper 11 may be the same as explained in conjunctionwith the first multilayered volume hologram structure of the invention.Upon removal of the release paper, the label is laminated at theadhesive layer 5 on a substrate 2 with a photograph, etc. pastedthereon, so that the multilayered volume hologram structure of FIG. 28can be obtained.

[0399] A label of FIG. 30(b) comprises an adhesive layer 5′, a volumehologram layer 6, a monomer or plasticizer-containing resin or brittlelayer 9, an adhesive layer 5″ and a surface protective film 7 laminatedon the release paper 11 in the described order. Upon removal of therelease paper 11, the label is laminated at the adhesive layer 5′ on acertificate or substrate 2 with a photograph, etc. pasted thereon, asshown in FIG. 29, so that a multilayered volume hologram structure isobtained.

[0400] In what follows, the seventh multilayered volume hologramstructure of the invention and the label for making the same will now beexplained with reference to illustrative examples 13, 14 and 15 whereinby “1%” is intended “% by weight”. ILLUSTRATIVE EXAMPLE 13

Preparation of Hologram-Recorded Material

[0401] A Lippmann hologram was recorded on a hologram recording film(Omnidex 706 made by Du Pont) comprising a multilayer construction ofpolyethylene terephthalate (PET) film/hologram recordingmaterial/polyvinyl chloride film. Upon removal of the polyvinyl chloridefilm from this multilayer construction, a film obtained by providing avinyl acetate resin layer containing 20% of phenoxy acrylate on apolyethylene terephthalate (PET) film was laminated on thehologram-recorded material, followed by a 120-minute heat treatment at120° C.

Preparation of Silicone Separator/Adhesive Layer

[0402] An adhesive agent (Nissetsu PE-118 made by Nippon Carbide Co.,Ltd.) was coated on a silicone separator (a 50 μm thick SP-SET made byTokyo Cellophane Paper Co., Ltd.) at a dry thickness of 10 μm.

Preparation of Surface Protective Film/Adhesive Layer/Silicone Separator

[0403] An adhesive agent (Nissetsu PE-118 made by Nippon Carbide Co.,Ltd.) was coated on a silicone separator (a 50 μm thick SP-SET made byTokyo Cellophane Paper Co., Ltd.) at a dry thickness of 10 μm, and apolyethylene terephthalate film (Lumirror T60 made by Toray Industries,Inc.) was laminated on the surface of the adhesive layer.

Preparation of Multilayered Volume Hologram Structure-Making Label

[0404] The aforesaid hologram-recorded material, from which thepolyvinyl chloride film was removed, was laminated on the aforesaidsilicone separator/adhesive layer to obtain a PETfilm/monomer-containing resin layer/hologram layer/adhesivelayer/silicone separator multilayer structure.

[0405] The PET film was removed from the multilayer structure while thesilicone separator was removed from the aforesaid surface protectivefilm/adhesive layer/silicone separator. Then, lamination was carried outto obtain the multilayered volume hologram structure-making label shownin FIG. 30(b), which comprised a surface protective film/adhesivelayer/monomer-containing resin layer/hologram layer/adhesivelayer/silicone separator structure.

Preparation of Multilayered Volume Hologram Structure

[0406] Upon a release of the silicone separator, the label was laminatedat the adhesive layer on a paper substrate with a photograph pastedthereon, as shown in FIG. 29.

[0407] After allowed to stand alone for 24 hours, the multi-layeredvolume hologram structure was forcibly delaminated. Consequently, themonomer-containing resin layer was released from the hologram layer attheir interface. Then, the hologram layer remaining on the substrate wasforcibly stripped therefrom. As a result, the hologram layer broke down.

ILLUSTRATIVE EXAMPLE 14

[0408] A multilayered volume hologram structure-making label and amultilayered volume hologram structure were prepared as in illustrativeexample 13 with the exception that the following hologram-recordedmaterial was used instead of the hologram-recorded material ofillustrative example 13.

Preparation of Hologram-Recorded Material

[0409] A Lippmann hologram was recorded on a hologram recording film(Omnidex 706 made by Du Pont) comprising a multilayer construction ofpolyethylene terephthalate (PET) film/hologram recordingmaterial/polyvinyl chloride film. Upon removal of the polyvinyl chloridefilm from this multilayer construction, a film obtained by providing anacrylic resin layer containing 30 parts by weight of 2-ethylhexylphthalate (DOP) (of 20 μm in thickness) on a polyethylene terephthalate(PET) film was laminated on the hologram-recorded material, followed bya 120° C. heat treatment for 120 hours.

[0410] After allowed to stand alone for 24 hours, the multi-layeredvolume hologram structure was forcibly delaminated. Consequently, theplasticizer-containing resin layer was released from the hologram layerat their interface. Then, the hologram layer remaining on the substratewas forcibly released therefrom. As a result, the hologram layer brokedown.

ILLUSTRATIVE EXAMPLE 15

[0411] A multilayered volume hologram structure-making label and amultilayered volume hologram structure were prepared as in illustrativeexample 13 with the exception that the following hologram-recordedmaterial was used instead of the hologram-recorded material ofillustrative example 13.

Preparation of Hologram-Recorded Material

[0412] A Lippmann hologram was recorded on a hologram recording mediumobtained by laminating a hydroxyethyl cellulose resin layer (of 20 μm inthickness) containing 20% of polystyrene beads, a hologram recordingmaterial layer (of 20 μm in thickness, and Omnidex 706 made by Du Pont)and a polyvinyl chloride film on a polyethylene terephthalate (PET)film.

[0413] After allowed to stand alone for 24 hours, the multi-layeredvolume hologram structure was forcibly delaminated. Consequently,delamination occurred in the brittle layer. Then, the hologram layerremaining on the substrate was forcibly stripped therefrom. As a result,the hologram layer broke down.

[0414] Next, the eighth multilayered volume hologram structure of theinvention and the label for making the same are explained.

[0415] The eighth multilayered volume hologram structure of theinvention is explained with reference to FIG. 1 that is a front view ofthe first multilayered volume hologram structure of the invention aswell as FIG. 31 that is a sectional view of the eighth multilayeredvolume hologram structure as taken along the A-A line in FIG. 1, FIG. 32that is a plan view of a pattern example of a patterned layer whereadhesion varies in a site-depending manner, FIG. 33 that is a sectionalview of another embodiment of the eighth multilayered volume hologramstructure, and FIG. 34 that is a sectional view of yet anotherembodiment of the eighth multilayered volume hologram structure. Inthese drawings, reference numeral 9 represents a patterned layer whereadhesion varies from site to site, and the same numerals as in FIG. 2indicate the same parts.

[0416] In the first embodiment of the eighth multilayered volumehologram structure of the invention, a personal information area orphotograph of face 4 is pasted on a substrate 2 with a photographicpaste 3, as shown in FIG. 31. A first adhesive layer 5′, a volumehologram layer 6, a patterned layer 9 with varying adhesion and asurface protective film 7 are laminated on the substrate 2 and astridethe personal information area or photograph of face 4.

[0417] The substrate 2, photographic paste 3, photograph of face orpersonal information area 4, adhesive layer 5′, and volume hologramlayer 6 may be the same as explained in conjunction with the firstmultilayered volume hologram structure of the invention, and theadhesive layer may be the same as explained in conjunction with thesixth multilayered volume hologram structure of the invention.

[0418] The surface protective film 7 may be the same as explained inconjunction with the first multilayered volume hologram structure of theinvention. When the patterned layer to be described later is a patternedrelease layer, the surface of the release layer, on which thehologram-recorded layer 6 is to be laminated, is preferably subjected toa primer treatment or adhesion-improving treatment, thereby improvingthe adhesion between the release layer and the hologram-recorded layer.When the patterned layer is formed of a primer layer or a layer alreadytreated for adhesion-improving purposes, however, such treatments may bedispensed with.

[0419] The primer treatment, for instance, may be achieved by thecoating of a resin such as silicone resin, acrylic resin, vinylchloride-vinyl acetate copolymer resin, nitrocellulose, polyester resin,and polyamide resin with an acid treating solution composed mainly ofphosphoric acid, and maleic acid or an alkali treating solution composedof shellac.

[0420] The adhesion-improving treatment, for instance, may be achievedby sandblasting, chemical etching, flame treatment, ozone treatment,corona discharge treatment, ultraviolet radiation curing treatment,electron beam treatment, radiation treatment, graft polymerization,plasma treatment, plasma graft polymerization, plasma polymerization,vacuum ultraviolet light treatment, and photopolymerization.

[0421] The patterned layer 9 is explained.

[0422] Between the volume hologram layer 6 and the surface protectivefilm 7 in the eighth multilayered volume hologram structure, there islocated the patterned layer 9 for allowing the adhesion between them tovary in a site-depending manner. In FIG. 32, the patterned layer 9 isshown in a bar code form, with reference numeral 9′ indicating anon-patterned zone. The patterned layer 9 may be provided not only in abar code form but also in a round spot or checked form; no particularlimitation is imposed on the shape of the patterned layer 9 if patternedand non-patterned zones are simultaneously provided on the volumehologram layer 6.

[0423] The patterned layer 9 may be formed of a release agent layerwhich facilitates a release of the surface protective layer 7.Alternatively or as an example, the patterned layer 9 may be obtained bysubjecting the surface of the surface protective film to a pattern-wiseprimer treatment or an adhesion-improving treatment.

[0424] The release agent layer may be formed by the pattern-wise coatingof a fluorine release agent, a silicone release agent, a stearaterelease agent, and a wax release agent. The adhesion-improving primerlayer may be formed by the pattern-wise coating of a resin such assilicone resin, acrylic resin, vinyl chloride-vinyl acetate copolymerresin, nitrocellulose, polyester resin, and polyamide resin with an acidtreating solution composed mainly of phosphoric acid, and maleic acid oran alkali treating solution composed of shellac. The adhesion-improvingtreatment, for instance, may be achieved by sandblasting, chemicaletching, flame treatment, ozone treatment, corona discharge treatment,ultraviolet radiation curing treatment, electron beam treatment,radiation treatment, graft polymerization, plasma treatment, plasmagraft polymerization, plasma polymerization, vacuum ultraviolet lighttreatment, and photopolymerization.

[0425] Instead of using the aforesaid patterned layer 9, it is alsoacceptable to treat the volume hologram layer and surface protectivefilm in such a manner that the mutual adhesion between them can beincreased or decreased upon irradiation with ultraviolet radiation orheating.

[0426] When, for instance, the hologram-recorded material or the surfaceprotective film material has a carbon-carbon double bond or a hydroxyl,amino, carboxyl, sulfone or mercapto group, the mutual adhesion betweenthe hologram layer and the surface protective film is increased upon theirradiation of them with ultraviolet radiation or the application ofheat thereto because covalent bonds or hydrogen bonds occur or increasebetween them. On the other hand, the mutual adhesion between thehologram layer and the surface protective film is decreased or lost by adecrease in the area of contact or an increase in the glass transitiontemperature due to polymerization reactions, etc.

[0427] Thus, the mutual adhesion between the volume hologram layer andthe surface protective film is increased or decreased upon theirradiation of them with ultraviolet radiation or the application ofheat thereto. To this end, the volume hologram layer and surfaceprotective film are exposed to ultraviolet radiation or heated in apattern-wise manner through a mask, so that the mutual adhesiontherebetween can vary between the exposed or heated regions and theunexposed or unheated regions.

[0428] If the first embodiment of the eighth multilayered volumehologram structure is delaminated for the purpose of falsification bymaking a photograph replacement, the volume hologram layer 6 wouldfracture into two portions, one portion at the exposed or heated regions9 being released together with the surface protective layer and theother portion at the unexposed or unheated regions 9′ remaining fixed onthe substrate side. This is because the volume hologram layer is formedof a soft material such as acrylic resin or gelatin. Even if the volumehologram layer 6 would not fracture into such portions, the recordedhologram image would discolor because of an elongation of the volumehologram layer either at the exposed or heated regions or at theunexposed or unheated regions. It is thus absolutely impossible to reusethe first embodiment of the eighth multilayered volume hologramstructure of the invention.

[0429] Another embodiment of the eighth multilayered volume hologramstructure of the invention is then explained with reference to FIG. 33.The second embodiment is similar to the aforesaid first embodiment withthe exception that the mutual adhesion between the volume hologram layerand the surface protective film is relatively decreased. To make up forthis, a second adhesive layer 5′ is interleaved between the volumehologram layer 6 and the surface protective film 7, as can be seen fromFIG. 33. A patterned layer 9 may be disposed between the second adhesivelayer 5″ and the surface protective film 7, as can be seen from FIG. 33.In this case, the patterned layer 9 may be the same as explained inconjunction with the first embodiment mentioned just above, and thesurface of the protective layer 7 to be laminated may be treated as inthe first embodiment.

[0430] Although not illustrated, the patterned layer 9 may be disposedbetween the volume hologram layer 6 and the second adhesive layer 5″. Inthis case, the patterned layer 9 may be formed of the same pattern formof release agent layer or primer layer as explained in conjunction withthe first embodiment, among which the release agent layer is preferred.Preferably, the surface of the protective film 7 is subjected to aprimer or adhesion-improving treatment for the purpose of improvingadhesion. When the surface protective film contains a plasticizer, it ispreferable to provide the second adhesive layer 5″, thereby protectingthe recorded hologram against the influence of the plasticizer.

[0431] In the second embodiment, too, the volume hologram layer 6 mayfracture into two portions, one portion at the exposed or heated regionsbeing released together with the surface protective film and the otherportion at the unexposed or unheated regions remaining fixed on thesubstrate side. It is thus absolutely impossible to reuse the volumehologram layer.

[0432] Yet another embodiment of the eighth multilayered volume hologramstructure of the invention is explained with reference to FIG. 34. Thisthird embodiment is similar to the aforesaid second embodiment with theexception that a patterned layer 9 is disposed between a first adhesivelayer 5′ and a volume hologram layer 6. The patterned layer 9 may be thesame pattern form of release agent layer or primer layer as explained inconjunction with the aforesaid first embodiment, among which the releaseagent layer is preferred. The surface of the protective film to belaminated is preferably subjected to a primer or adhesion-improvingtreatment for the purpose of enhancing adhesion. It is here to be notedthat the second adhesive layer 5″ is provided while both the adhesionbetween the surface protective film and the volume hologram layer andthe adhesion between the substrate and the volume hologram layer aretaken into consideration. When the adhesion of the volume hologram layeris high, the second adhesive layer 5″ may be dispensed with.

[0433] Although not illustrated, the patterned layer 9 may be locatedbetween the first adhesive layer 5′ and a photograph 4 or personalinformation area 4′. In this case, the patterned layer 9 may be formedof the same pattern form of release agent layer or primer layer asexplained in conjunction with the first embodiment, among which therelease agent layer is preferred. Preferably, the surface of theprotective film to be laminated is subjected to a primer oradhesion-improving treatment for the purpose of enhancing adhesion. Whenthe surface protective film contains a plasticizer, it is preferable toprovide the second adhesive layer 5″, thereby protecting the recordedhologram against the influence of the plasticizer.

[0434] In the third embodiment, too, the volume hologram layer 6 mayfracture into two portions, one portion at the exposed or heated regionsbeing released together with the surface protective film and the otherportion at the unexposed or unheated regions remaining fixed on thesubstrate side. It is thus absolutely impossible to reuse the volumehologram layer.

[0435] Throughout the first to third embodiments mentioned above, it ispreferable that the adhesive layers, volume hologram layer, patternedlayer for achieving varying adhesion from site to site and the surfaceprotective film are all excellent in transparency. Especially if thepatterned layer 9 is transparent, it is then possible to achieve everhigher security.

[0436] A label for making the eighth multilayered volume hologramstructure of the invention is explained with reference to FIGS. 36(a),36(b) and 36(c) that are sectional views of the multilayer constructionsthereof.

[0437] In FIGS. 36(a), 36(b) and 36(c), reference numerals 10 and 11represent a multilayered volume hologram structure-making label and arelease paper, respectively, and the same numerals as in FIGS. 31 to 33indicate the same parts.

[0438] The first embodiment of the label for making the eighthmultilayered volume hologram structure of the invention is applied tothe fabrication of the first embodiment of the eighth multilayeredvolume hologram structure of the invention. As shown in FIG. 36(a), alabel 10 comprises a first adhesive layer 5′, a volume hologram layer 6,a patterned layer 9 for achieving varying adhesion from site to site anda surface protective film 7 laminated on the release paper 11 in thedescribed order.

[0439] The release paper 11 may be the same as explained in conjunctionwith the first embodiment of the eighth multilayered volume structurementioned above. Upon removal of the release paper, the label islaminated at the first adhesive layer 5′ on a substrate 2 with aphotograph, etc. pasted thereon, so that the multilayered volumehologram structure shown in FIG. 31 can be obtained.

[0440] A label of FIG. 36(b) is a second embodiment of the label formaking the eighth multilayered volume hologram structure, and comprisesa first adhesive layer 5′, a volume hologram layer 6, a second adhesivelayer 5″, a patterned layer 9 for achieving varying adhesion from siteto site and a surface protective film 7 laminated on the release paper11 in the described order. The release paper and so on may be the sameas mentioned above.

[0441] A label 10, from which the release paper 11 is removed, islaminated at the first adhesive layer 5′ on a substrate 2 with aphotograph, etc. pasted thereof, so that the multilayered volumehologram structure shown in FIG. 33 can be obtained.

[0442] A label of FIG. 36(c) is a third embodiment of the label formaking the eighth multilayered volume hologram structure, and comprisesa first adhesive layer 5′, a patterned layer 9 for achieving varyingadhesion from site to site, a volume hologram layer 5, a second adhesivelayer 5″ and a surface protective film 7 laminated on the release paper11 in the described order. The release paper and so on may be the sameas mentioned above.

[0443] A label 10, from which the release paper 11 is removed, islaminated at the first adhesive layer 5′ on a substrate 2 with aphotograph, etc. pasted thereof, so that the multilayered volumehologram structure shown in FIG. 34 can be obtained.

[0444] In what follows, the eighth multilayered volume hologramstructure of the invention and the label for making the same will now beexplained with reference to illustrative examples 16 to 20.

ILLUSTRATIVE EXAMPLE 16 Preparation of Hologram-Recorded Layer

[0445] A Lippmann hologram was recorded on a hologram recording filmobtained by laminating a hologram recording material (a 20 μm thickOmnidex 706M made by Du Pont) and a polyethylene terephthalate (PET)film of 25 μm in thickness on a polyethylene terephthalate (PET) film of50 μm in thickness in the described order. Thereafter, the 25 μm thickPET film was removed from the hologram-recorded material, and a PET filmcoated with a polyvinyl acetate layer was laminated on the surface ofthe hologram-recorded material, followed by a 24-minute heating at 120°C.

Preparation of Surface Protective Film/Patterned Layer/Volume HologramLayer/PET Film

[0446] A silicone release agent (KE-42TS made by The Shin-Etsu ChemicalCo., Ltd.) was pattern coated on a transparent surface protective film(a 25 μm thick PET film) at a post-drying thickness of 1 μm, as shown inFIG. 32, thereby obtaining a patterned layer comprising an array oftreated and untreated regions. This patterned layer was laminated on thesurface of the volume hologram layer exposed by releasing the PET filmcoated with a polyvinyl acetate layer from the hologram-recorded layer,thereby obtaining a surface protective film/patterned layer/volumehologram layer/PET film, which was then heated at 120° C. for 60 minutesfor bonding.

Preparation of Silicone Separator A/First Adhesive Layer/SiliconeSeparator B

[0447] An acrylic adhesive agent (Nissetsu PE-118 made by Nippon CarbideCo., Ltd.) was coated on a silicone separator A (a 50 μm thick SP-PET05made by Tokyo Cellophane Paper Co., Ltd.) at a dry thickness of 15 μm,and a silicone separator B (a 50 μm thick SP-PET02 made by TokyoCellophane Paper Co., Ltd.) was laminated on the adhesive layer.

Preparation of Multilayered Volume Hologram Structure-Making Label

[0448] The PET film was removed from the surface protectivefilm/patterned layer/volume hologram layer/PET film while the siliconeseparator A was removed from the silicone separator A/first adhesivelayer/silicone separator B. Then, lamination was carried out to obtain amultilayered volume hologram structure-making label comprising a surfaceprotective film/patterned layer/volume hologram layer/first adhesivelayer/silicone separator B.

Preparation of Multilayered Volume Hologram Structure

[0449] Upon a release of the silicone separator B, the thus obtainedmultilayered volume hologram structure-making label was laminated at thefirst adhesive layer on a paper substrate with a photograph, etc. pastedthereon, as shown in FIG. 31, thereby obtaining a multilayered volumehologram structure according to the invention.

[0450] After allowed to stand alone for 24 hours, the hologram label wasforcibly stripped from the paper substrate. At the patterned regions,the surface protective film could be easily released, but the hologramlayer broke down at the non-patterned regions because it was releasedfollowing the surface protective film. It was thus absolutely impossibleto reuse the volume hologram layer.

ILLUSTRATIVE EXAMPLE 17 Preparation of Hologram-Recorded Layer

[0451] A Lippmann hologram was recorded on a hologram recording film(Omnidex 706 made by Du Pont) obtained by laminating a hologramrecording material layer and a polyvinyl chloride (PVC) film on apolyethylene terephthalate (PET) film in the described order.Thereafter, the PVC film was removed from the hologram recording film,and a PET film coated with a polyvinyl acetate layer was laminated onthe hologram recording material, followed by a 24-minute heating at 120°C.

Preparation of Surface Protective Film/Patterned Layer/Second AdhesiveLayer/Silicone Separator

[0452] An acrylic adhesive agent (Nissetsu PE-118 made by Nippon CarbideCo., Ltd.) was coated on a silicone separator (a 50 μm thick SP-PET05made by Tokyo Cellophane Paper Co., Ltd.) at a dry thickness of 15 μm.

[0453] On the other hand, a silicone release agent (KE-42TS made by TheShin-Etsu Chemical Co., Ltd.) was pattern coated on a stretchedpolypropylene film (a 30 μm thick OPP film, OPU-1 made by TokyoCellophane Paper Co., Ltd.) at a post-drying thickness of 1 μm as inillustrative example 16, and then was laminated on the adhesive layer ofthe acrylic adhesive layer/silicone separator obtained as just mentionedabove to obtain a surface protective film/patterned layer/secondadhesive layer/silicone separator multilayer structure.

Preparation of Surface Protective Film/Patterned Layer/Second AdhesiveLayer/Volume Hologram Layer/PET film

[0454] The PET film coated with a polyvinyl acetate layer was removedfrom the hologram-recorded layer while the silicone separator wasremoved from the surface protective film/patterned layer/second adhesivelayer/silicone separator multilayer structure. Then, lamination wascarried out to obtain a surface protective film/patterned layer/secondadhesive layer/volume hologram layer/PET film mutlilayer structure.

Preparation of Multilayered Volume Hologram Structure-Making Label

[0455] The PET film was removed from the surface protectivefilm/patterned layer/second adhesive layer/volume hologram layer/PETfilm while the silicone separator A was removed from the siliconeseparator A/first adhesive layer/silicone separator B prepared inillustrative example 16. Then, lamination was carried out to obtain amultilayered volume hologram structure-making label comprising a surfaceprotective film/patterned layer/second adhesive layer/volume hologramlayer/first adhesive layer/silicone separator B multilayer structure.

[0456] This multilayered volume hologram structure-making label was usedas in illustrative example 16 to make a multilayered volume hologramstructure. The hologram label was forcibly stripped from the papersubstrate as in illustrative example 16. At the patterned regions, thesurface protective film could be easily released, but the hologram layerbroke down at the non-patterned regions because it was releasedfollowing the surface protective film. It was thus absolutely impossibleto reuse the volume hologram layer.

ILLUSTRATIVE EXAMPLE 18 Preparation of Hologram-Recorded Layer

[0457] A Lippmann hologram was recorded on a hologram recording film(Omnidex 706 made by Du Pont) obtained by laminating a hologramrecording material layer and a polyvinyl chloride (PVC) film on apolyethylene terephthalate (PET) film in the described order.Thereafter, the PVC film was removed from the hologram-recorded layer,and a re-releasable acrylic adhesive film (Sanitechto H225E made bySanei Kaken Co., Ltd.) was laminated on the hologram-recorded material,followed by a 24-minute heating at 120° C.

Preparation of Surface Protective Film/Second Adhesive Layer/SiliconeSeparator

[0458] An acrylic adhesive agent (Nissetsu PE-118 made by Nippon CarbideCo., Ltd.) was coated on a silicone separator (a 50 μm thick SP-PET05made by Tokyo Cellophane Paper Co., Ltd.) at a dry thickness of 15 μm.Then, a stretched polypropylene film (a 30 μm thick OPP film, OPU-1 madeby Tokyo Cellophane Paper Co., Ltd.) was laminated on the acrylicadhesive layer.

Preparation of Surface Protective Film/Second Adhesive Layer/VolumeHologram Layer/PET Film

[0459] The silicone separator was removed from the surface protectivefilm/second adhesive layer/silicone separator obtained as mentionedabove while the re-releasable acrylic adhesive film was removed from thehologram-recorded layer obtained as mentioned above. Then, laminationwas carried out to obtain a surface protective film/second adhesivelayer/volume hologram layer/PET film.

Preparation of Silicone Separator B/First Adhesive Layer/PatternedLayer/Silicone Separator A

[0460] An acrylic adhesive agent (Nissetsu PE-118 made by Nippon CarbideCo., Ltd.) was coated on a silicone separator B (a 50 μm thick SP-PET02made by Tokyo Cellophane Paper Co., Ltd.) at a dry thickness of 15 μm.

[0461] A silicone release agent (KE-42TS made by The Shin-Etsu ChemicalCo., Ltd.) was pattern coated on a silicone separator A (a 50 μm thickSP-PET05 made by Tokyo Cellophane Paper Co., Ltd.) at a post-dryingthickness of 1 μm as in illustrative example 16, and then laminated onthe adhesive layer of the acrylic adhesive layer/silicone separatorobtained as just mentioned above to obtain a silicone separator B/firstadhesive layer/patterned layer/silicone separator A multilayerstructure.

Preparation of Multilayered Volume Hologram Structure-Making Label

[0462] The PET film was removed from the surface protective film/secondadhesive layer/volume hologram layer/PET film obtained as mentionedabove while the silicone separator A was removed from the siliconeseparator B/first adhesive layer/patterned layer/silicone separator Aobtained as mentioned above. Then, lamination was carried out to obtaina multilayered volume hologram structure-making label comprising asurface protective film/second adhesive layer/volume hologramlayer/patterned layer/first adhesive layer/silicone separator B.

[0463] This multilayered volume hologram structure-making label was usedas in illustrative example 16 to make a multilayered volume hologramstructure. The hologram label was forcibly stripped from the papersubstrate as in illustrative example 16. At the patterned regions, thehologram label could be easily released, but the hologram layer brokedown at the non-patterned regions because it was released following thesurface protective film. It was thus absolutely impossible to reuse thevolume hologram layer.

ILLUSTRATIVE EXAMPLE 19 Preparation of Hologram-Recorded Layer

[0464] A Lippmann hologram was recorded on a hologram recording film(Omnidex 706M made by Du Pont) obtained by laminating a hologramrecording material layer and a polyethylene terephthalate film (a 25 μmthick PET film) on a polyethylene terephthalate film (a 50 μm thick PETfilm) in the described order, followed by removal of the 25 μm thick PETfilm. Apart from this, a PP film was removed from a color tuning film(CTF 75 made by Du Pont) comprising a PET film (25 μm)/color tuning film(about 20 μm)/polypropylene film (PP film) multilayer structure. Then,this color tuning film was laminated on the hologram recording materiallayer of the hologram-recorded layer, followed by a 12-minute heating at120° C. The multilayer structure obtained in this case was composed of aPET film (50 μm)/hologram layer/color tuning layer/PET film (25 μm).

Preparation of Partially Corona Treated Surface Protective Film/SecondAdhesive Layer/Silicone Separator

[0465] A partially corona treated OPP film was prepared by coronatreating a stretched polypropylene film (a 20 mm thick OPP film made byTokyo Cellophane Paper Co., Ltd.) through a Teflon resin mask in such amanner that a masked portion was corona treated and an unmasked portionwas not.

[0466] An acrylic adhesive agent (Nissetsu PE-118 made by Nippon CarbideCo., Ltd.) was coated on a silicone separator (a 50 μm thick SP-PET05made by Tokyo Cellophane Paper Co., Ltd.) at a dry thickness of 20 μm.Then, the partially corona treated OPP film was laminated on theadhesive layer.

Preparation of Partially Corona Treated Surface Protective Film/SecondAdhesive Layer/Volume Hologram Layer/Color Tuning Film Layer/PET Film

[0467] The silicone separator was removed from the surface protectivefilm/silicone separator obtained as mentioned above while the 50 μmthick PET film was removed from the hologram-recorded layer obtained asmentioned above. Then, lamination was carried out to obtain a partiallycorona treated surface protective film/second adhesive layer/volumehologram layer/color tuning film layer/PET film (25 μm) multilayeredstructure.

Preparation of Silicone Separator A/First Adhesive Layer/SiliconeSeparator B

[0468] An acrylic adhesive agent (Nissetsu PE-118 made by Nippon CarbideCo., Ltd.) was coated on a silicone separator A (a 50 μm thick SP-PET05made by Tokyo Cellophane Paper Co., Ltd.) at a dry thickness of 20 μm.

[0469] A silicone separator B (a 50 μm thick SP-PET02 made by TokyoCellophane Paper Co., Ltd.) subjected to a release treatment on bothsurfaces was laminated on the adhesive layer to obtain a siliconeseparator A/first adhesive layer/silicone separator B.

Preparation of Mutlilayered Volume Hologram Structure-Making Label

[0470] The color tuning film layer/PET film (25 μm) was removed from thesurface protective film/second adhesive layer/volume hologramlayer/color tuning film layer/PET film (25 μm) obtained as mentionedabove while the silicone separator A was removed from the siliconeseparator A/first adhesive layer/silicone separator B obtained asmentioned above. Then, lamination was carried out to obtain a partiallycorona treated surface protective film/second adhesive layer/volumehologram layer/patterned layer/first adhesive layer/silicone separatorB.

[0471] This multilayered volume hologram structure-making label was usedas in illustrative example 16 to obtain a multilayered volume hologramstructure. The hologram label was forcibly stripped from the papersubstrate as in illustrative example 16. The hologram in the volumehologram layer broke down because of a large adhesion strengthdifference between the corona treated region and the untreated region.It was thus absolutely impossible to reuse the volume hologram layer.

ILLUSTRATIVE EXAMPLE 20 Preparation of Hologram-Recorded Layer

[0472] A Lippmann hologram was recorded on a hologram recording filmobtained by laminating a hydroxyl group-containing hologram recordingmaterial layer (of 20 μm in thickness; a product made by Du Pont) and anethylene-vinyl alcohol copolymer film (EVOH film) laminated on apolyethylene terephthalate film (PET film) in the described order. Thehologram recording film was patterned by irradiating and heating theEVOH film with far infrared radiation using a mask. Further, thehologram recording film was uniformly irradiated all over the surfacewith ultraviolet radiation to obtain a surface protective film/patternedlayer/volume hologram layer/PET film multilayer structure, with apartial adhesive force difference between the surface protective filmand the volume hologram layer.

[0473] At the heated positions, the interaction due to hydrogen bondsbetween the EVOH film and the hologram recording material is increasedso that the adhesion therebetween can be enhanced. As a result, there isobtained a multilayered structure comprising a surface protective film,a hologram layer in partial contact with the surface protective film anda PET film, with a partial adhesion strength difference between thesurface protective film and the hologram layer.

Preparation of Silicone Separator A/First Adhesive Layer/SiliconeSeparator B

[0474] An acrylic adhesive agent (Nissetsu PE-118 made by Nippon CarbideCo., Ltd.) was coated on a silicone separator A (a 50 μm thick SP-PET05made by Tokyo Cellophane Paper Co., Ltd.) at a dry thickness of 20 μm.

[0475] A silicone separator B (a 50 μm thick SP-PETB2 made by TokyoCellophane Paper Co., Ltd.) subjected to a release treatment on bothsurfaces was laminated on the adhesive layer to obtain a siliconeseparator A/first adhesive layer/silicone separator B.

Preparation of Multilayered Volume Hologram Structure-Making Label

[0476] The PET film (25 μm) was removed from the partial contact surfaceprotective film/volume hologram layer/PET film (25 μm) obtained asmentioned above while the silicone separator A was removed from thesilicone separator A/first adhesive layer/silicone separator B obtainedas mentioned above. Then, lamination was carried out to obtain a partialcontact surface protective film/volume hologram layer/first adhesivelayer/silicone separator B.

[0477] This multilayered volume hologram structure-making label was usedas in illustrative example 16 to obtain a multilayered volume hologramstructure. The hologram label was forcibly stripped from the papersubstrate as in illustrative example 16. The hologram in the volumehologram layer broke down because of a large adhesion strength variationbetween the sites subjected to the partial contact treatment and thesites not subjected. It was thus absolutely impossible to reuse thevolume hologram layer.

APPLICABILITY OF THE INVENTION TO INDUSTRY

[0478] The present invention is to determine whether or not a volumehologram image bonded to an ID card or other certificate with aphotograph and a personal information area pasted thereof has brokedown, thereby preventing falsification of the ID card. When the volumehologram layer is forcibly stripped off for the purpose of making aphotograph replacement or falsifying the personal information area, thevolume hologram layer can break down certainly. This makes it possibleto provide a multilayered volume hologram structure according to which aphotograph replacement or falsification of an information area isabsolutely impossible, and a label for making the same.

What we claim is:
 1. A multilayered volume hologram structure comprisinga substrate for a certificate or the like, and a re-bondable adhesivelayer, a volume hologram layer and a surface protective film laminatedon said substrate in the described order, characterized in that a peelstrength, with which a multilayer structure consisting of said volumehologram layer and said surface protective film is peeled from saidsubstrate, is greater than a breaking strength or a tensile strength at1% elongation of said structure consisting of said volume hologram layerand said surface protective film.
 2. The multilayered volume hologramstructure according to claim 1, characterized in that the peel strength,with which said multilayer structure consisting of said volume hologramlayer and said surface protective film is peeled from said substrate, is0.1 Kg/25 mm to 5.0 Kg/25 mm, and a multilayer structure consisting ofsaid re-bondable adhesive layer, said volume hologram layer and saidsurface protective film has a breaking strength or a tensile strength at1% elongation of 0.01 Kg/mm2 to 5.0 Kg/mm².
 3. The multilayered volumehologram structure according to claim 1 or 2, characterized in thatanother re-bondable adhesive layer is interleaved between said volumehologram layer and said surface protective film.
 4. The multilayeredvolume hologram structure according to any one of claims 1 to 3,characterized in that said surface protective film is subjected to ahard coat treatment on a surface thereof.
 5. The multilayered volumehologram structure according to any one of claims 1 to 4, characterizedin that said surface protective film is subjected to a release treatmenton a surface thereof.
 6. A label used for making a multilayered volumehologram structure as recited in claim 1, characterized by comprising arelease paper and a re-bondable adhesive layer, a volume hologram layerand a surface protective film laminated on said release paper in thedescribed order, said label being pasted on a substrate for acertificate or the like upon removal of said release paper.
 7. Themultilayered volume hologram structure-making label according to claim6, characterized in that a peel strength, with which a multilayerstructure consisting of said volume hologram layer and said surfaceprotective film is peeled from said substrate, is 0.1 Kg/25 mm to 5.0Kg/25 mm, and a multilayer structure consisting of said re-bondableadhesive layer, said volume hologram layer and said surface protectivefilm has a breaking strength or a tensile strength at 1% elongation of0.01 Kg/mm2 to 5.0 Kg/mm².
 8. The multilayered volume hologramstructure-making label according to claim 6 or 7, characterized in thatanother re-bondable adhesive layer is interleaved between said volumehologram layer and said surface protective film.
 9. A multilayeredvolume hologram structure comprising a substrate, and a first adhesivelayer, a volume hologram layer, a second adhesive layer and a surfaceprotective film laminated on said substrate in the described order,characterized in that said second adhesive layer is weaker in adhesionthan said first adhesive layer, and when said surface protective film isreleased from said multilayered volume hologram structure in a givenreleasing direction, a releasing line is produced in a direction atright angles with respect to said releasing direction.
 10. Amultilayered volume hologram structure comprising a substrate, and athird adhesive layer, a colored sheet, a first adhesive layer, a volumehologram layer, a second adhesive layer and a surface protective filmlaminated on said substrate in the described order, characterized inthat said second adhesive layer is weaker in adhesion than said firstadhesive layer and said third adhesive layer, and when said surfaceprotective film is released from said multilayered volume hologramstructure in a given releasing direction, a releasing line is producedin a direction at right angles with respect to said releasing direction.11. The multilayered volume hologram structure according to claim 1 or2, characterized in that a peel strength, with which said surfaceprotective film is released from said multilayered volume hologramstructure, is 0.001 Kg/25 mm to 0.1 Kg/25 mm, and a peel strengthbetween said substrate and said volume hologram layer is 0.1 Kg/25 mm to5.0 Kg/25 mm.
 12. The multilayered volume hologram structure accordingto any one of claims 9 to 11, characterized in that said volume hologramlayer is made up of a photosensitive material used for recording a drytype of volume phase hologram, which comprises a matrix polymer, aphoto-polymerizable compound, a photopolymerization initiator, and asensitizing dye.
 13. A label used for making a multilayered volumehologram structure as recited in claim 9 and comprising a release paper,and a first adhesive layer, a volume hologram layer, a second adhesivelayer and a surface protective film laminated on said release paper inthe described order, characterized in that said second adhesive layer isweaker in adhesion than said first adhesive layer, and when said surfaceprotective film is released from said multilayered volume hologramstructure in a given releasing direction, a releasing line is producedin a direction at right angles with respect to said releasing direction.14. A label used for making a multilayered volume hologram structure asrecited in claim 10 and comprising a release paper, and a third adhesivelayer, a colored sheet, a first adhesive layer, a volume hologram layer,a second adhesive layer and a surface protective film laminated on saidsubstrate in the described order, characterized in that said secondadhesive layer is weaker in adhesion than said first adhesive layer andsaid third adhesive layer, and when said surface protective film isreleased from said multilayered volume hologram structure in a givenreleasing direction, a releasing line is produced in a direction atright angles with respect to said releasing direction.
 15. Amulti-layered volume hologram structure comprising a substrate for acertificate or the like, and a heat sealing layer, a volume hologramlayer, an adhesive layer and a surface protective film laminated on saidsubstrate, characterized in that the whole surface of said multilayeredvolume hologram structure is heat sealed.
 16. A multilayered volumehologram structure comprising a substrate for a certificate or the like,and an adhesive layer, a volume hologram layer, a heat sealing layer anda surface protective layer laminated on said substrate, characterized inthat said volume hologram layer and an end portion thereof are coveredwith said surface protective film, said volume hologram layer islaminated on said substrate, and only a whole peripheral end of saidmultilayered volume hologram structure including a whole peripheral endof said volume hologram layer is heat sealed.
 17. The multilayeredvolume hologram structure according to claim 15 or 16, characterized inthat said heat sealing has been done at 100° C. to 180° C.
 18. A labelused for making a multilayered volume hologram structure as recited inclaim 15, characterized by comprising a release paper, and a heatsealing layer, a volume hologram layer, an adhesive layer and a surfaceprotective layer laminated on said release paper in the described order.19. A label used for making a multilayered volume hologram structure asrecited in claim 16, characterized by comprising a release paper, and anadhesive layer, a volume hologram layer, a heat sealing layer and asurface protective film laminated on said release paper in the describedorder, a size of said surface protective film being such that, upon saidlabel laminated on a substrate for a certificate or the like, saidsurface protective film covers said volume hologram layer including awhole periphery of an end thereof.
 20. A multilayered volume hologramstructure, characterized by comprising a substrate and a hologram layerpasted on said substrate, said hologram layer being provided with asurface-protective film on a surface thereof, and further including asecond adhesive layer for bonding together said surface protective filmand said hologram layer and a first adhesive layer for bonding togethersaid hologram layer and said substrate, either one of said adhesivelayers having an adhesive force profile in its own plane.
 21. A labelused for making a multilayered volume hologram structure as recited inclaim 20, characterized by comprising a release paper, and a firstadhesive layer, a volume hologram layer, a second adhesive layer and asurface protective film laminated on said release paper in the describedorder, said label being pasted on a substrate for a certificate or thelike upon removal of said release paper therefrom, and either one ofsaid first adhesive layer and said second adhesive layer having anadhesive force profile in its own plane.
 22. A multilayered volumehologram structure comprising a substrate, and a first adhesive layer, avolume hologram layer, a second adhesive layer and a surface protectivefilm laminated on said substrate in the described order, characterizedin that microcapsules, each encapsulated with a material capable ofbreaking said hologram layer, are incorporated in said adhesive layers,so that said microcapsules can break down upon delamination of saidmultilayered volume hologram structure.
 23. A multilayered volumehologram structure comprising a substrate, and a third adhesive layer, acolored sheet, a first adhesive layer, a volume hologram, a secondadhesive layer and a surface protective film laminated on said substratein the described order, characterized in that microcapsules, eachencapsulated with a material capable of breaking said volume hologramlayer, are incorporated in said first and second adhesive layersdisposed adjacent to said volume hologram layer, so that saidmicrocapsules can break down upon delamination of said multilayeredvolume hologram structure.
 24. The fifth multilayered volume hologramstructure according to claim 22 or 23, characterized in that a materialforming said volume hologram layer comprises a matrix polymer, aphotopolymerizable compound, a photopolymerization initiator and asensitizing dye, and said material capable of breaking said volumehologram layer comprises an organic solvent having a solubilizing actionon said volume hologram layer forming material and/or a plasticizerhaving a swelling action on said volume hologram layer forming material.25. A label used for making a multilayered volume hologram structure asrecited in claim 22 and comprising a release paper, and a first adhesivelayer, a volume hologram layer, a second adhesive layer and a surfaceprotective film laminated on said release paper in the described order,characterized in that microcapsules, each encapsulated with a materialcapable of breaking said volume hologram layer, are incorporated in saidadhesive layers, so that said microcapsules can break down upondelamination of said multilayered volume hologram structure.
 26. A labelused for making a multilayered volume hologram structure as recited inclaim 23 and comprising a release paper, and a third adhesive layer, acolored sheet, a first adhesive layer, a volume hologram, a secondadhesive layer and a surface protective film laminated on said releasepaper in the described order, characterized in that microcapsules, eachencapsulated with a material capable of breaking said volume hologramlayer, are incorporated in said adhesive layers disposed adjacent tosaid volume hologram layer, so that said microcapsules can break downupon delamination of said multilayered volume hologram structure. 27.The multilayered volume hologram structure-making label according toclaim 25 or 26, characterized in that a material forming said volumehologram layer comprises a matrix polymer, a photopolymerizablecompound, a photo-polymerization initiator and a sensitizing dye, andsaid material capable of breaking said volume hologram layer comprisesan organic solvent having a solubilizing action on said volume hologramlayer forming material and/or a plasticizer having a swelling action onsaid volume hologram layer forming material.
 28. A multilayered volumehologram structure, characterized by comprising a substrate for acertificate or the like, and an adhesive layer, a volume hologram layercontaining fine particles having an average primary particle size of 1nm to 100 nm and used in an amount of 10 parts by weight to 100 parts byweight per 100 parts by weight of a photosensitive material, and asurface protective film laminated on said substrate in the describedorder.
 29. The multilayered volume hologram structure according to claim28, characterized in that said fine particles are each a fluorescentfine particle emitting fluorescence upon irradiation with ultravioletradiation.
 30. A multilayered volume hologram structure, characterizedby comprising a substrate for a certificate or the like, and an adhesivelayer, a volume hologram layer containing plastic particles or glassbeads having a refractive index substantially equal to that of aphotosensitive material and used in an amount of 10 parts by weight to100 parts by weight per 100 parts by weight of said photosensitivematerial, and a surface protective film laminated on said substrate inthe described order.
 31. The multilayered volume hologram structureaccording to any one of claims 28 to 30, characterized in that saidvolume hologram layer and said surface protective film are laminatedtogether with an additional adhesive layer interleaved therebetween. 32.A label used for making a multilayered volume hologram structure asrecited in claim 28, characterized by comprising a release paper, and anadhesive layer, a volume hologram layer containing fine particles havingan average primary particle size of 1 nm to 100 nm and used in an amountof 10 parts by weight to 100 parts by weight per 100 parts by weight ofa photosensitive material, and a surface protective film laminated onsaid release paper in the described order.
 33. The multilayered volumehologram structure-making label according to claim 32, characterized inthat said fine particles are each a fluorescence fine particle emittingfluorescence upon irradiation with ultraviolet radiation.
 34. A labelused for making a multilayered volume hologram structure as recited inclaim 30, characterized by comprising a release paper, and an adhesivelayer, a volume hologram layer containing plastic particles or glassbeads having a refractive index substantially equal to that of aphotosensitive material and used in an amount of 10 parts by weight to100 parts by weight per 100 parts by weight of said photosensitivematerial, and a surface protective film laminated on said substrate inthe described order.
 35. The multilayered volume hologramstructure-making label according to any one of claims 32 to 34,characterized in that said volume hologram layer and said surfaceprotective film are laminated together with an additional adhesive layerinterleaved therebetween.
 36. A multilayered volume hologram structure,characterized by comprising a substrate for a certificate or the like,and an adhesive layer, a volume hologram layer, a resin layer containinga monomer or a plasticizer and a surface protective film laminated onsaid substrate in the described order.
 37. The multilayered volumehologram structure according to claim 36, characterized in that saidmonomer or plasticizer-containing resin layer and said surfaceprotective film are laminated together with an additional adhesive layerinterleaved therebetween.
 38. A multilayered volume hologram structure,characterized by comprising a substrate for a certificate or the like,and an adhesive layer, a volume hologram layer, a brittle layer, anadhesive layer and a surface protective film laminated on said substratein the described order.
 39. A label used for making a multilayeredvolume hologram structure as recited in claim 36, characterized bycomprising a release paper, and an adhesive layer, a volume hologramlayer, a resin layer containing a monomer or a plasticizer and a surfaceprotective film laminated on said release paper in the described order.40. The multilayered volume hologram structure-making label according toclaim 39, characterized in that said monomer or plasticizer-containingresin layer and said surface protective film are laminated together withan additional adhesive layer interleaved therebetween.
 41. Themultilayered volume hologram structure-making label according to claim39, characterized by comprising a release paper, and an adhesive layer,a volume hologram layer, a brittle layer, an adhesive layer and asurface protective film laminated on said release in the describedorder.
 42. A multilayered volume hologram structure, characterized bycomprising a substrate for a certificate or the like, and a firstadhesive layer, a volume hologram layer and a surface protective filmlaminated on said substrate in the described order, and furtherincluding between said volume hologram layer and said surface protectivefilm a patterned area for varying mutual adhesion between said volumehologram layer and said surface protective film in a site-dependentmanner, so that upon an intentional release of a multilayer structurefrom said substrate, said volume hologram layer is broken or elongatedwhile said volume hologram layer is separated into a portion adhering toa substrate side and a portion adhering to a surface protective filmside.
 43. The multilayered volume hologram structure according to claim42, characterized in that upon irradiation with ultraviolet radiation orheating, one of said volume hologram layer or said surface protectivefilm shows adhesion to the other or the mutual adhesion between saidvolume hologram layer and said surface protective film decreases.
 44. Amultilayered volume hologram structure, characterized by comprising asubstrate for a certificate or the like, and a first adhesive layer, avolume hologram layer, a second adhesive layer and a surface protectivefilm laminated on said substrate in the described order, and furtherincluding between said second adhesive layer and said surface protectivefilm a patterned area for varying mutual adhesion between said secondadhesive layer and said surface protective film in a site-dependentmanner, so that upon an intentional release of a multilayer structurefrom said substrate, said volume hologram layer is broken or elongatedwhile said volume hologram layer is separated into a portion adhering toa substrate side and a portion adhering to a surface protective filmside.
 45. The multilayered volume hologram structure according to anyone of claims 42 to 44, characterized in that said patterned area forvarying said adhesion in a site-dependent manner is a pattern form ofrelease agent layer.
 46. The multilayered volume hologram structureaccording to any one of claims 42 to 45, characterized in that a surfaceof said surface protective film to be laminated is provided with aprimer layer for enhancing adhesion.
 47. The multilayered volumehologram structure according to any one of claims 42 to 45,characterized in that said patterned area for varying said adhesion in asite-dependent manner is an adhesion-enhancing pattern form of primerlayer.
 48. The multilayered volume hologram structure according to anyone of claims 42 to 44, characterized in that said patterned area forvarying said adhesion in a site-dependent manner is obtained by treatinga surface of said surface protective film to be laminated in such a waythat said surface is easily bondable.
 49. A multilayered volume hologramstructure of the invention, characterized by comprising a substrate fora certificate or the like, and a first adhesive layer, a volume hologramlayer, a second adhesive layer and a surface protective film laminatedon said substrate in the described order, and further including betweensaid first adhesive layer and said volume hologram layer a patternedarea for varying mutual adhesion between said first adhesive layer andsaid volume hologram layer in a site-dependent manner, so that upon anintentional release of a multilayer structure from said substrate, saidvolume hologram layer is broken or elongated while said volume hologramlayer is separated into a portion adhering to a substrate side and aportion adhering to a surface protective film side.
 50. A label used formaking a multilayered volume hologram structure as recited in claim 42,characterized by comprising a release paper, and a first adhesive layer,a volume hologram layer and a surface protective film laminated on saidsubstrate in the described order, and further including between saidvolume hologram layer and said surface protective film a patterned areafor varying mutual adhesion between said volume hologram layer and saidsurface protective film in a site-dependent manner, said label beingpasted on a substrate for a certificate or the like upon a release ofsaid release paper therefrom.
 51. A label used for making a multilayeredvolume hologram structure as recited in claim 44, characterized bycomprising a release paper, and a first adhesive layer, a volumehologram layer, a second adhesive layer and a surface protective filmlaminated on said substrate in the described order, and furtherincluding between said second adhesive layer and said surface protectivefilm a patterned area for varying mutual adhesion between said secondadhesive layer and said surface protective film in a site-dependentmanner, said label being pasted on a substrate for a certificate or thelike upon a release of said release paper therefrom.
 52. A label usedfor making a multilayered volume hologram structure as recited in claim49, characterized by comprising a release paper, and a first adhesivelayer, a volume hologram layer, a second adhesive layer and a surfaceprotective film laminated on said substrate in the described order, andfurther including between said first adhesive layer and said volumehologram layer a patterned area for varying mutual adhesion between saidfirst adhesive layer and said volume hologram layer in a site-dependentmanner, said label being pasted on a substrate for a certificate or thelike upon a release of said release paper therefrom.